Free OBD2 code lookup

What does your fault code mean?

A diagnostic trouble code (DTC) is your car’s way of saying something needs attention. This lookup covers the most common OBD2 codes: plain-language meanings, severity and what to do next.

P0010 Camshaft position actuator circuit (Bank 1) Engine / phases Medium severity

Fault in the variable valve timing (VVT) control circuit — the engine may run unevenly, and fuel consumption may increase.

Symptoms

  • Uneven idling
  • reduced power
  • increased fuel consumption

Common causes

  • Contaminated or old engine oil
  • a stuck VVT valve
  • a stretched chain

Estimated repair cost20–250 €

What to do: Check the VVT solenoid valve, its connection and the oil level — contaminated oil is the most common cause.

P0011 The intake shaft phase is too far advanced (Bank 1) Engine / phases Medium severity

The position of the camshaft does not match the signal from the control unit — often due to oil pressure or the VVT valve.

Symptoms

  • Uneven idling
  • reduced power
  • increased fuel consumption

Common causes

  • Contaminated or old engine oil
  • a stuck VVT valve
  • a stretched chain

Estimated repair cost20–250 €

What to do: Change the oil and the filter, and check the VVT valve. If the problem persists, check the chain tensioner.

P0012 The intake shaft phase is too far behind (Bank 1) Engine / phases Medium severity

The VVT system is unable to reach the set position — uneven running, loss of power.

Symptoms

  • Uneven idling
  • reduced power
  • increased fuel consumption

Common causes

  • Contaminated or old engine oil
  • a stuck VVT valve
  • a stretched chain

Estimated repair cost20–250 €

What to do: Check the oil level and quality, the VVT valve and the phase sensor.

P0014 The exhaust camshaft phase is set too far forward (Bank 1) Engine / phases Medium severity

Exhaust camshaft phase control deviation.

Symptoms

  • Uneven idling
  • reduced power
  • increased fuel consumption

Common causes

  • Contaminated or old engine oil
  • a stuck VVT valve
  • a stretched chain

Estimated repair cost20–250 €

What to do: As with other VVT codes — oil, VVT valve, phase sensor.

P0016 Mismatch between the positions of the crankshaft and the camshaft (Bank 1, Sensor A) Engine / Phases High severity

The crankshafts are out of synchronisation — a chain or belt tooth may have jumped.

Symptoms

  • Difficult starting
  • rattling noise from the engine
  • emergency mode

Common causes

  • Stretched timing chain
  • worn tensioner
  • skipped tooth
  • oil pressure problems

Estimated repair cost300–1200 €

What to do: Check the timing chain/belt and tensioner immediately — it is dangerous to drive.

P0017 Mismatch between the positions of the crankshaft and camshaft (Bank 1, Sensor B) Engine / phases High severity

Same as P0016, but on the exhaust shaft side.

Symptoms

  • Difficult starting
  • rattling noise from the engine
  • emergency mode

Common causes

  • Stretched timing chain
  • worn tensioner
  • skipped tooth

Estimated repair cost300–1200 €

What to do: Check the distribution mechanism before continuing to use the machine.

P0087 Pressure in the fuel line is too low Fuel system High severity

The fuel pressure is lower than specified — this may be due to a failing pump or a blocked filter.

Symptoms

  • Power drop under load
  • jerks
  • emergency mode

Common causes

  • Clogged fuel filter
  • failing fuel pump
  • faulty pressure regulator

Estimated repair cost40–450 €

What to do: Check the fuel filter, the pump capacity and the pressure regulator.

P0088 Excessive pressure in the fuel line Fuel system High severity

The fuel pressure is above the limit — this is usually caused by a fault in the pressure regulator or sensor.

Symptoms

  • The ‘Check Engine’ light is on
  • the engine is running unevenly
  • the vehicle may be in emergency mode

Common causes

  • Pressure control valve stuck
  • main line pressure sensor faulty

Estimated repair cost80–350 €

What to do: Check the pressure control valve and the main line pressure sensor.

P0101 Airflow (MAF) sensor signal out of range Air intake Medium severity

The measured air volume does not match the expected value — inaccurate mixture, misfiring.

Symptoms

  • Uneven idling
  • lack of power
  • excessive smoke

Common causes

  • Contaminated MAF sensor
  • leak behind the sensor
  • blocked air filter

Estimated repair cost15–200 €

What to do: Clean the MAF sensor with a special cleaner and check for any leaks beneath the sensor.

P0102 The airflow (MAF) sensor signal is too low Air intake Medium severity

An MAF signal at the lower limit is a sign of a faulty sensor, wiring harness or blocked filter.

Symptoms

  • Poor acceleration
  • the engine may cut out
  • emergency mode

Common causes

  • MAF is dirty or faulty
  • a connection has come loose
  • a cable is damaged

Estimated repair cost15–200 €

What to do: Check the air filter and the sensor connection, and clean the sensor.

P0103 The airflow (MAF) sensor signal is too high Air intake Medium severity

The MAF is showing an unrealistically high flow rate — this is usually due to a sensor fault.

Symptoms

  • Rough running
  • ‘Check Engine’ light is on

Common causes

  • Faulty MAF sensor
  • short circuit in the wiring harness

Estimated repair cost80–200 €

What to do: Clean or replace the MAF sensor.

P0106 Manifold pressure (MAP) sensor signal out of range Air intake Medium severity

The MAP sensor reading does not comply with the operating conditions — the mixture and ignition calculations are inaccurate.

Symptoms

  • Uneven running
  • increased costs
  • power fluctuations

Common causes

  • A broken or blocked vacuum hose
  • a faulty MAP sensor

Estimated repair cost15–120 €

What to do: Check the MAP sensor’s vacuum hose and connector.

P0113 The signal from the intake air temperature sensor is too high Air intake Low severity

The IAT sensor circuit is showing an open circuit (high voltage).

Symptoms

  • The ‘Check Engine’ light is on
  • the car is harder to start when cold in winter

Common causes

  • Faulty IAT sensor
  • disconnected connector
  • broken cable

Estimated repair cost20–150 €

What to do: Check the sensor connection and wiring; the sensor is often integrated into the MAF.

P0115 Fault in the coolant temperature sensor circuit Cooling Medium severity

The ECT sensor signal is unstable — this may cause problems with cold starts and fan control.

Symptoms

  • Inaccurate temperature reading
  • fan running continuously
  • difficult cold start

Common causes

  • Faulty ECT sensor
  • damaged connector
  • air lock in the cooling system

Estimated repair cost20–90 €

What to do: Check the sensor and its connection.

P0117 The coolant temperature sensor signal is too low Cooling Medium severity

A short circuit in the circuit — the control unit detects an unrealistically high temperature.

Symptoms

  • The fan is running continuously
  • the mixture is too lean for a cold engine

Common causes

  • A short circuit in the sensor circuit
  • a faulty sensor

Estimated repair cost20–90 €

What to do: Check the cable and the sensor.

P0118 Coolant temperature sensor signal is too high Cooling Medium severity

A break in the circuit — the unit detects an unrealistically low temperature and enriches the mixture.

Symptoms

  • Difficult cold start
  • increased costs

Common causes

  • Sensor circuit open
  • disconnected connector
  • faulty sensor

Estimated repair cost20–90 €

What to do: Check the sensor connection; replace the sensor.

P0128 The engine is not reaching operating temperature Cooling Low severity

The thermostat is probably stuck in the open position — this results in longer heating times and higher running costs.

Symptoms

  • The engine takes a long time to warm up
  • the cabin heating is less effective
  • higher running costs

Common causes

  • The thermostat is stuck in the open position
  • rarely — a sensor fault

Estimated repair cost40–180 €

What to do: Replace the thermostat.

P0130 Fault in the O2 sensor circuit (1 block, 1 sensor) Exhaust gas control Medium severity

The signal from the front lambda sensor is outside the specified range — the air-fuel mixture is not being adjusted correctly.

Symptoms

  • Increased fuel consumption
  • rough running
  • ‘Check Engine’ light on

Common causes

  • Out-of-date lambda sensor
  • damaged cable
  • exhaust leak upstream of the sensor

Estimated repair cost80–250 €

What to do: Check the sensor connection; replace the old sensor.

P0133 The O2 sensor is responding too slowly (1 block, 1 sensor) Exhaust gas control Medium severity

An out-of-date lambda sensor can no longer keep up with changes in the air-fuel mixture.

Symptoms

  • Increased fuel consumption
  • sluggish response to the accelerator

Common causes

  • Out-of-date lambda sensor
  • sensor contaminated with soot

Estimated repair cost80–250 €

What to do: Replace the front lambda sensor.

P0135 Fault in the O₂ sensor heater circuit (1 block, 1 sensor) Exhaust gas control Low severity

The sensor heating is not working — while the sensor is cold, the mixture is controlled approximately.

Symptoms

  • The ‘Check Engine’ light is on
  • slightly higher fuel consumption when the engine is cold

Common causes

  • The sensor heater has blown
  • a cable is damaged
  • a fuse has blown

Estimated repair cost60–180 €

What to do: Check the heater’s fuse and connection; the sensor is the part that needs replacing most often.

P0141 Fault in the O₂ sensor heater circuit (block 1, sensor 2) Exhaust gas control Low severity

Fault with the rear (behind the catalytic converter) sensor heater.

Symptoms

  • The ‘Check Engine’ light is on
  • slightly higher fuel consumption when the engine is cold

Common causes

  • The sensor heater has blown
  • a cable is damaged
  • a fuse has blown

Estimated repair cost60–180 €

What to do: As with P0135 — rear sensor only.

P0171 The mixture is too thin (1 block) Fuel system Medium severity

The system is forced to constantly enrich the mixture — the most common cause is a leak in the intake system or the MAF sensor.

Symptoms

  • Uneven running
  • jerking when accelerating
  • ‘Check Engine’ light on

Common causes

  • Leaky intake
  • dirty MAF sensor
  • weak fuel pump
  • blocked filter

Estimated repair cost20–300 €

What to do: Check for intake leaks behind the throttle valve, and check the MAF and fuel pressure.

P0172 The mixture is too rich (1 block) Fuel system Medium severity

Excessive fuel — possible causes include leaking injectors, high fuel pressure or a dirty MAF sensor.

Symptoms

  • Black smoke
  • the smell of fuel
  • increased costs

Common causes

  • Leaking injectors
  • fuel pressure too high
  • dirty MAF sensor
  • thermostat constantly stuck closed

Estimated repair cost40–350 €

What to do: Check the injectors, the pressure regulator and the MAF sensor.

P0174 The mixture is too lean (Bank 2) Fuel system Medium severity

Same as P0171, but only in the second cylinder bank (V-type engines).

Symptoms

  • Uneven running
  • jerking when accelerating
  • ‘Check Engine’ light on

Common causes

  • Leaky intake
  • dirty MAF sensor
  • weak fuel pump
  • blocked filter

Estimated repair cost20–300 €

What to do: The same causes as for P0171 — often, both codes together indicate a general air leak.

P0175 The mixture is too rich (Bank 2) Fuel system Medium severity

As P0172 in the second row.

Symptoms

  • Black smoke
  • the smell of fuel
  • increased costs

Common causes

  • Leaking injectors
  • fuel pressure too high
  • dirty MAF sensor
  • thermostat constantly stuck closed

Estimated repair cost40–350 €

What to do: See P0172.

P0201 Fault in the circuit of the No. 1 cylinder injector Fuel system High severity

If the injector’s electrical circuit is open or short-circuited, the cylinder may fail to operate.

Symptoms

  • One cylinder is not firing
  • severe vibration
  • smell of fuel

Common causes

  • Loose nozzle connection
  • broken wire
  • damaged cable

Estimated repair cost40–300 €

What to do: Check the nozzle connection, resistance and wiring.

P0300 Detection of random / multi-cylinder misfires Inflammation High severity

The engine is missing strokes in several cylinders — it’s jerking and the CEL is flashing. There is a risk of damage to the catalytic converter.

Symptoms

  • The engine is shaking, particularly when idling
  • the ‘Check Engine’ light is flashing
  • loss of power

Common causes

  • Worn-out spark plugs
  • a broken ignition coil
  • a weak injector
  • low compression

Estimated repair cost30–250 €

What to do: Check the spark plugs, ignition coils, fuel pressure and compression. Do not drive far with the CEL light flashing.

P0301 Misfires in cylinder 1 Inflammation High severity

Leaks have been identified specifically in cylinder 1.

Symptoms

  • The engine is shaking, particularly when idling
  • the ‘Check Engine’ light is flashing
  • loss of power

Common causes

  • Worn-out spark plugs
  • a broken ignition coil
  • a weak injector
  • low compression

Estimated repair cost30–250 €

What to do: Swap the spark plug / coil with another cylinder — if the fault code ‘moves’, you’ve found the culprit.

P0302 Misfires in cylinder 2 Inflammation High severity

Misfires detected in cylinder 2.

Symptoms

  • The engine is shaking, particularly when idling
  • the ‘Check Engine’ light is flashing
  • loss of power

Common causes

  • Worn-out spark plugs
  • a broken ignition coil
  • a weak injector
  • low compression

Estimated repair cost30–250 €

What to do: See method P0301.

P0303 Misfires in cylinder 3 Inflammation High severity

Misfires detected in cylinder 3.

Symptoms

  • The engine is shaking, particularly when idling
  • the ‘Check Engine’ light is flashing
  • loss of power

Common causes

  • Worn-out spark plugs
  • a broken ignition coil
  • a weak injector
  • low compression

Estimated repair cost30–250 €

What to do: See method P0301.

P0304 Misfires in the 4-cylinder engine Inflammation High severity

Misfires detected in cylinder 4.

Symptoms

  • The engine is shaking, particularly when idling
  • the ‘Check Engine’ light is flashing
  • loss of power

Common causes

  • Worn-out spark plugs
  • a broken ignition coil
  • a weak injector
  • low compression

Estimated repair cost30–250 €

What to do: See method P0301.

P0325 Fault in the detonation sensor circuit (Bank 1) Inflammation Medium severity

If the knock sensor is not working, the engine delays ignition for safety reasons — resulting in a drop in power.

Symptoms

  • Reduced power
  • higher costs
  • possible metal grinding under load

Common causes

  • Faulty detonation sensor
  • loose mounting
  • damaged cable

Estimated repair cost50–180 €

What to do: Check the sensor connection and tightening torque; replace the sensor.

P0335 Fault in the crankshaft position sensor circuit Engine / sensors High severity

Without this signal, the engine may fail to start at all or cut out whilst driving.

Symptoms

  • The engine won't start or cuts out whilst driving
  • jerking

Common causes

  • Faulty crankshaft sensor
  • damaged wiring harness
  • damaged toothed disc

Estimated repair cost40–160 €

What to do: Check the sensor, its clearance and the wiring.

P0340 Fault in the camshaft position sensor circuit Engine / sensors High severity

The synchronisation of the injectors and ignition is disrupted — the engine is difficult to start and may stall.

Symptoms

  • Difficulty starting
  • the engine may cut out
  • jerking

Common causes

  • Faulty sensor
  • damaged cable
  • incorrect clearance
  • damaged signal disc

Estimated repair cost40–150 €

What to do: Check the sensor and the connector; make sure the signal disc is not damaged.

P0341 Camshaft position sensor signal out of range Engine / sensors Medium severity

There is a signal, but it does not match the expected one — a distribution deviation is possible.

Symptoms

  • Difficulty starting
  • the engine may cut out
  • jerking

Common causes

  • Faulty sensor
  • damaged cable
  • incorrect clearance
  • damaged signal disc

Estimated repair cost40–150 €

What to do: Check the sensor and the distribution phases.

P0351 A fault in the primary/secondary circuit of the ignition coil Inflammation High severity

A fault in the control circuit for a specific reel — the cylinder is not operating.

Symptoms

  • One cylinder is not firing
  • severe vibration
  • the ‘Check Engine’ light is flashing

Common causes

  • Blown fuse
  • disconnected connector
  • damaged control cable

Estimated repair cost40–160 €

What to do: Check the coil connection; replace the coil.

P0400 Flow restriction in the EGR system Exhaust gas control Medium severity

Exhaust gas recirculation is not working properly.

Symptoms

  • Uneven idling
  • smoke
  • loss of power

Common causes

  • EGR valve or ducts blocked by soot
  • faulty vacuum control

Estimated repair cost80–400 €

What to do: Clean the EGR valve and ducts to remove any deposits.

P0401 Insufficient EGR flow Exhaust gas control Medium severity

A clogged EGR valve or EGR passages — a common problem with diesel engines.

Symptoms

  • ‘Check Engine’ light on
  • elevated NOx levels
  • sluggish performance

Common causes

  • Clogged EGR valve
  • calcified channels
  • low vacuum

Estimated repair cost80–400 €

What to do: Clean or replace the EGR valve; check the vacuum control.

P0402 Excessive EGR flow Exhaust gas control Medium severity

The EGR valve is stuck open — this causes rough idling, and the engine may stall.

Symptoms

  • Uneven idling
  • the engine may cut out
  • excessive smoke

Common causes

  • The stuck EGR valve has been opened
  • there is soot on the seat

Estimated repair cost80–400 €

What to do: Clean or replace the EGR valve.

P0420 Catalyst efficiency below the threshold (Bank 1) Exhaust gas control Medium severity

The catalytic converter is no longer purifying the exhaust gases as it should — or the rear sensor is giving a false reading.

Symptoms

  • The ‘Check Engine’ light is on
  • no other symptoms are noticeable, or there is a loss of power

Common causes

  • Worn-out catalytic converter
  • out-of-date rear sensor
  • exhaust leak
  • prolonged misfires

Estimated repair cost250–900 €

What to do: First of all, check the rear lambda sensor and make sure there are no leaks; if there are, the catalytic converter will need replacing.

P0430 Catalyst efficiency below the threshold (Bank 2) Exhaust gas control Medium severity

Same as P0420, but only in the second cylinder bank.

Symptoms

  • The ‘Check Engine’ light is on
  • reduced power

Common causes

  • Worn-out catalytic converter
  • out-of-date rear sensor
  • exhaust leak

Estimated repair cost250–900 €

What to do: See P0420.

P0440 EVAP system fault Exhaust gas control Low severity

The fuel vapour recovery system is leaking or not working — this is usually a minor issue that poses no danger.

Symptoms

  • The ‘Check Engine’ light is on
  • there’s a smell of fuel near the tank

Common causes

  • The fuel tank cap is not tightened
  • cracked hoses
  • a faulty valve

Estimated repair cost0–150 €

What to do: First of all, check that the fuel cap is tightly closed.

P0441 EVAP purge flow obstruction Exhaust gas control Low severity

The blow-off valve is not working or is not operating at the correct time.

Symptoms

  • The ‘Check Engine’ light is on

Common causes

  • Faulty blow-off valve
  • blocked hose

Estimated repair cost30–120 €

What to do: Check the purge valve and its hoses.

P0442 A small leak has been detected in the EVAP system Exhaust gas control Low severity

A small leak in the fuel vapour system.

Symptoms

  • The ‘Check Engine’ light is on
  • there is a faint smell of fuel

Common causes

  • Leaky fuel tank cap
  • cracked hose
  • corrosion-damaged filler neck

Estimated repair cost10–200 €

What to do: Fuel tank cap, hoses, valves — a smoke test is often required.

P0455 A major leak has been detected in the EVAP system Exhaust gas control Low severity

A major source of leakage is usually a tank cap that has not been tightened properly or is damaged.

Symptoms

  • The ‘Check Engine’ light is on
  • there’s a smell of petrol

Common causes

  • The fuel cap is loose or damaged
  • a hose has come off
  • the fuel tank is damaged

Estimated repair cost10–250 €

What to do: Screw the cap on / replace it, and delete the code.

P0456 A very small leak has been detected in the EVAP system Exhaust gas control Low severity

A barely noticeable steam leak.

Symptoms

  • The ‘Check Engine’ light is on

Common causes

  • Microscopic vapour leakage — lid gasket, hoses, valves

Estimated repair cost10–200 €

What to do: Like P0442 — this is usually only detected by a smoke test.

P0500 Fault with the vehicle speed sensor (VSS) Speed sensors Medium severity

If the speed signal is missing or inaccurate, gear changes and the speedometer reading may be affected.

Symptoms

  • The speedometer is not working or is fluctuating
  • jolts when changing gears

Common causes

  • Faulty speed sensor
  • damaged cable
  • dashboard issue

Estimated repair cost40–150 €

What to do: Check the VSS sensor and its circuit.

P0505 Fault in the idle speed control system Idling Medium severity

Unstable or incorrect idle speed.

Symptoms

  • Unstable idle speed
  • the engine may cut out when stationary

Common causes

  • Clogged throttle valve
  • faulty idle valve
  • air leak

Estimated repair cost20–200 €

What to do: Clean the throttle and the idle valve.

P0562 System voltage too low Electrical system Medium severity

The problem with the charging system is that either the alternator or the battery is failing.

Symptoms

  • Dim light
  • difficult to start
  • battery warning light is on

Common causes

  • A failing alternator
  • an old battery
  • poor ground connections
  • a worn-out belt

Estimated repair cost30–350 €

What to do: Check the alternator output, the battery and the earth connections.

P0563 System voltage too high Electrical system Medium severity

The generator regulator is supplying too high a voltage — this is dangerous for electronic equipment.

Symptoms

  • Light bulbs may blow
  • electronic faults may occur

Common causes

  • Faulty alternator voltage regulator

Estimated repair cost80–350 €

What to do: Check the generator’s voltage regulator immediately.

P0601 Internal memory error in the engine control unit Control units High severity

The ECU’s self-test has detected an internal fault.

Symptoms

  • The ‘Check Engine’ light is on
  • various malfunctions may occur

Common causes

  • Internal ECU memory fault
  • voltage spikes
  • moisture in the unit

Estimated repair cost150–600 €

What to do: Sometimes reprogramming helps; often the unit needs to be repaired or replaced.

P0603 Control Unit Memory (KAM) error Control units Medium severity

Settings may be lost — often after the battery has been disconnected or due to a weak power supply.

Symptoms

  • Loss of trim
  • uneven running after start-up

Common causes

  • The battery has been disconnected
  • low battery
  • intermittent power supply

Estimated repair cost0–150 €

What to do: Check the battery and power circuits; the calibration will be reset.

P0605 Control unit ROM error Control units High severity

Internal software memory error.

Symptoms

  • The ‘Check Engine’ light is on
  • the vehicle may be in emergency mode

Common causes

  • ECU software memory error
  • update failed

Estimated repair cost150–600 €

What to do: Try resetting it; if the problem persists, replace the unit.

P0606 Control unit processor error Control units High severity

ECU processor self-test error.

Symptoms

  • ‘Check Engine’ light on
  • erratic performance
  • emergency mode

Common causes

  • ECU processor fault
  • power supply or ground issues

Estimated repair cost150–600 €

What to do: Check the power supply and ground connections; if the problem persists, the unit needs repairing.

P0700 Transmission control system fault (general code) Transmission Medium severity

The gearbox module has detected a fault — this code simply ‘calls for’ further diagnostics.

Symptoms

  • ‘Box on fire’ warning
  • jolts when switching gears
  • emergency mode

Common causes

  • See the codes in the box section — the reason is there

Estimated repair cost50–2000 €

What to do: Scan the gearbox module separately — you’ll find the exact code there.

P0705 Gear position sensor (PRNDL) fault Transmission Medium severity

The gearbox ‘does not know’ which gear is engaged — this may lead to problems with starting and changing gears.

Symptoms

  • Will not start from P
  • incorrect gear is displayed
  • gear selector lever is locked

Common causes

  • The selector switch sensor is faulty or out of adjustment
  • damaged wires

Estimated repair cost60–250 €

What to do: Check the selector switch and its adjustment.

P0715 Fault with the turbine/intake speed sensor Transmission Medium severity

The gearbox control loses the input speed signal — impact, emergency mode.

Symptoms

  • Jerking when changing gear
  • emergency mode
  • inaccurate speedometer

Common causes

  • Faulty rev counter
  • damaged cable
  • metal shavings in the oil

Estimated repair cost60–300 €

What to do: Check the sensor and the wiring; check the oil in the gearbox.

P0730 Incorrect gear ratio Transmission High severity

The actual power transmission does not match the selected gear — the clutch or belt is slipping.

Symptoms

  • High revs without increasing speed
  • skidding
  • impacts

Common causes

  • Low or old gearbox oil
  • worn friction clutches
  • solenoid failure

Estimated repair cost100–2500 €

What to do: Check the gearbox oil level and condition; next, have the gearbox diagnosed at a service centre.

P0740 Fault in the torque converter lock-up circuit Transmission Medium severity

The converter lock-up isn’t working — higher fuel consumption, higher revs on the motorway.

Symptoms

  • Higher fuel consumption on the motorway
  • higher revs
  • vibration

Common causes

  • Faulty lock-up solenoid
  • old oil
  • worn-out converter

Estimated repair cost100–1200 €

What to do: Gearbox oil and solenoids — at the garage.

P0741 The momentum converter lock-up is ineffective / causes a hang Transmission Medium severity

The converter clutch slips or fails to engage.

Symptoms

  • Vibration at a constant speed
  • higher costs

Common causes

  • Slipping converter clutch
  • solenoid fault
  • old oil

Estimated repair cost100–1200 €

What to do: See P0740.

P0299 Insufficient turbine pressure (underboost) Turbine Medium severity

The turbo system is not reaching the set pressure — loss of power, emergency mode.

Symptoms

  • Weak suction
  • emergency mode
  • whistling

Common causes

  • Leaky pressure hoses
  • jammed VNT geometry
  • faulty control mechanism
  • worn-out turbine

Estimated repair cost50–1200 €

What to do: Check for pressure leaks in the hoses and the intercooler, and check the control valve (wastegate / VNT).

P0234 Excessive turbine pressure (overboost) Turbine High severity

If the pressure exceeds the limit, the control mechanism will jam. This may cause damage to the engine.

Symptoms

  • Sudden power cut
  • emergency mode

Common causes

  • Stuck VNT / wastegate mechanism
  • faulty pressure sensor

Estimated repair cost50–800 €

What to do: Check the VNT mechanism / wastegate and the vacuum control system. Avoid heavy loads.

P0068 The MAP/MAF readings do not correspond to the throttle position Air intake Medium severity

The sensor readings contradict one another — this is often due to air leakage.

Symptoms

  • Lack of power
  • uneven running

Common causes

  • Leaky intake
  • dirty throttle valve
  • MAF or MAP fault

Estimated repair cost20–250 €

What to do: Check the intake system for leaks, the MAF and MAP sensors, and the throttle.

P0121 Throttle position sensor signal out of range Throttle Medium severity

The TPS signal is out of range — power restrictions or emergency mode may be in effect.

Symptoms

  • Limited revs
  • emergency mode
  • sluggish response to the accelerator pedal

Common causes

  • Worn-out throttle potentiometer
  • dirty throttle valve
  • requires adjustment

Estimated repair cost30–350 €

What to do: Check the throttle assembly and carry out throttle calibration.

P0122 Throttle position sensor signal is too low Throttle Medium severity

A short circuit to earth in the TPS circuit.

Symptoms

  • Emergency mode
  • high idle speed

Common causes

  • Short circuit in the TPS circuit
  • disconnected connection

Estimated repair cost30–350 €

What to do: Check the cable and the sensor.

P0220 Fault in circuit B of the throttle position sensor Throttle Medium severity

Fault on the second TPS track — the electronic throttle valve switches to emergency mode.

Symptoms

  • Emergency mode
  • limited power

Common causes

  • Fault in the throttle assembly
  • damaged wiring harness

Estimated repair cost80–400 €

What to do: Inspection / replacement and adjustment of the throttle assembly.

P0507 Idle speed is higher than expected Idling Low severity

Increased idle speed — air leak or a dirty throttle valve.

Symptoms

  • Idle speed is too high

Common causes

  • Air leak in the intake
  • dirty throttle valve
  • adjustment required

Estimated repair cost20–150 €

What to do: Clean the throttle, check the hoses and carry out the adjustment.

P0305 Misfires in cylinder 5 Inflammation High severity

Faults detected in cylinder 5.

Symptoms

  • The engine is shaking, particularly when idling
  • the ‘Check Engine’ light is flashing
  • loss of power

Common causes

  • Worn-out spark plugs
  • a broken ignition coil
  • a weak injector
  • low compression

Estimated repair cost30–250 €

What to do: See method P0301.

P0306 Misfires in the 6-cylinder engine Inflammation High severity

Misfires detected in cylinder 6.

Symptoms

  • The engine is shaking, particularly when idling
  • the ‘Check Engine’ light is flashing
  • loss of power

Common causes

  • Worn-out spark plugs
  • a broken ignition coil
  • a weak injector
  • low compression

Estimated repair cost30–250 €

What to do: See method P0301.

P2002 The efficiency of the diesel particulate filter (DPF) is below the threshold Exhaust gas control Medium severity

The DPF is no longer filtering as it should — it is either blocked or damaged.

Symptoms

  • Weaker traction
  • frequent recharging
  • increased costs

Common causes

  • Clogged DPF
  • faulty pressure differential sensor
  • frequent short journeys

Estimated repair cost100–1200 €

What to do: Try a forced regeneration; check the pressure differential sensor.

P2463 DPF — excessive soot build-up Exhaust gas control High severity

The filter is clogged with soot; regeneration no longer takes place automatically.

Symptoms

  • Significant loss of power
  • emergency mode
  • DPF warning light on

Common causes

  • DPF full
  • regeneration not taking place
  • city mode

Estimated repair cost100–1200 €

What to do: Forced regeneration or filter cleaning at a service centre. Avoid making only short journeys.

P2015 Fault with the intake manifold valve position sensor Air intake Medium severity

The position of the variable-geometry (swirl) manifold valves is incorrect — a common issue in VW/Audi diesel engines.

Symptoms

  • The engine runs roughly at low revs
  • the ‘Check Engine’ light is on

Common causes

  • Broken throttle lever mechanism
  • faulty gearbox
  • soot

Estimated repair cost100–500 €

What to do: Check the valve mechanism and the motor; the manifold is often replaced or the lever mechanism repaired.

P0403 Fault in the EGR control circuit Exhaust gas control Medium severity

Fault in the EGR valve’s electrical control circuit.

Symptoms

  • The ‘Check Engine’ light is on
  • the EGR is not working

Common causes

  • Faulty EGR actuator
  • broken control cable
  • blown fuse

Estimated repair cost80–350 €

What to do: Check the valve actuator and wiring.

P0245 The turbine wastegate solenoid signal is too low Turbine Medium severity

Fault in the pressure control solenoid circuit.

Symptoms

  • Reduced power
  • ‘Check Engine’ light is on

Common causes

  • Faulty control solenoid
  • broken hose
  • damaged cable

Estimated repair cost40–200 €

What to do: Check the solenoid and the hoses.

P1000 OBD system readiness cycles are incomplete Control units Low severity

Information code — the system has not yet completed its self-test following the clearing of faults or the disconnection of the battery.

Symptoms

  • None — information code

Common causes

  • Codes have recently been cleared or the battery has been disconnected

Estimated repair cost0 €

What to do: Just drive as normal — the code will clear itself.

B0001 Fault in the driver’s front airbag control circuit Safety airbags High severity

The SRS module has detected a fault in the driver’s airbag circuit — the airbag may not deploy.

Symptoms

  • The SRS / airbag warning light is on

Common causes

  • A loose connection under the seat
  • a damaged coiled cable
  • a faulty airbag module

Estimated repair cost50–400 €

What to do: Safety system — leave it to the service centre. A common cause: a connection under the seat or a coiled cable in the steering column.

B0010 Fault in the passenger front airbag control circuit Safety airbags High severity

The problem with the passenger airbag chain.

Symptoms

  • The SRS / airbag warning light is on

Common causes

  • A loose connection under the seat
  • a damaged coiled cable
  • a faulty airbag module

Estimated repair cost50–400 €

What to do: For servicing — usually the connector under the seat or the headrest module.

B0020 Fault in the left-hand side airbag control circuit Safety airbags High severity

The problem with the side cushion chain.

Symptoms

  • The SRS / airbag warning light is on

Common causes

  • A loose connection under the seat
  • a damaged coiled cable
  • a faulty airbag module

Estimated repair cost50–400 €

What to do: SRS diagnostics at the service centre.

B0028 Fault in the control circuit of the right-hand side airbag Safety airbags High severity

The problem with the side cushion chain.

Symptoms

  • The SRS / airbag warning light is on

Common causes

  • A loose connection under the seat
  • a damaged coiled cable
  • a faulty airbag module

Estimated repair cost50–400 €

What to do: SRS diagnostics at the service centre.

B0050 Fault in the driver’s seatbelt sensor Seat belts Medium severity

The seatbelt buckle sensor is indicating an error.

Symptoms

  • The SRS warning light is on
  • the seatbelt indicator is showing an error

Common causes

  • Fault in the seatbelt microswitch
  • disconnected connector under the seat
  • damaged wires

Estimated repair cost30–150 €

What to do: Check the buckle connection; it is often the buckle’s microswitch itself that is at fault.

B0070 Fault in the driver’s seatbelt tensioner circuit Seat belts High severity

The problem with the pyrotechnic tensioner circuit is that the belt may not deploy fully in the event of an accident.

Symptoms

  • The SRS warning light is on
  • the seatbelt indicator is showing an error

Common causes

  • Fault in the seatbelt microswitch
  • disconnected connector under the seat
  • damaged wires

Estimated repair cost30–150 €

What to do: SRS component — for service use only.

B0100 Front impact sensor fault SRS sensors High severity

Problem with the impact sensor signal — the airbags may not deploy correctly.

Symptoms

  • The SRS warning light is on

Common causes

  • Faulty impact sensor
  • damaged connector
  • sensor not replaced following an accident

Estimated repair cost60–250 €

What to do: Check the sensor connections; the sensor is replaced following minor faults.

B1000 Internal fault in the body/SRS control unit Control units High severity

The unit’s self-monitoring system has detected an internal fault.

Symptoms

  • The SRS or body system warning lights are on
  • the relevant functions are not working

Common causes

  • Internal fault in the unit
  • moisture
  • voltage surges

Estimated repair cost100–500 €

What to do: Try deleting it; if the problem recurs, the block will need to be repaired or replaced.

B1318 Low battery voltage Electrical system Medium severity

The body module detects an excessively low supply voltage — a common cause of fault codes.

Symptoms

  • Various random errors
  • slow start-up

Common causes

  • An old battery
  • a weak alternator
  • poor ground connections

Estimated repair cost30–300 €

What to do: Check the battery and its charge; clear any fault codes.

B1352 Fault in the ignition key circuit Ignition lock Medium severity

Circuit fault: ‘key inserted’ in the lock.

Symptoms

  • Key recognition is not working
  • the ignition indicator light is not on

Common causes

  • Worn-out lock contact assembly
  • damaged wires

Estimated repair cost40–200 €

What to do: Check the lock’s connections.

B1422 Fault in the rear window heating circuit Electrical accessories Low severity

The rear window heating isn't working.

Symptoms

  • The rear window isn't heating up

Common causes

  • Blown fuse
  • faulty relay
  • broken heating elements

Estimated repair cost10–120 €

What to do: Check the fuse, the relay and the windscreen heating strip terminals.

B1600 No signal is being received from the key transponder Immobiliser High severity

The immobiliser cannot detect the key chip — the engine will not start.

Symptoms

  • The engine won’t start
  • the immobiliser light is flashing

Common causes

  • Damaged key chip
  • faulty antenna around the lock

Estimated repair cost40–200 €

What to do: Try the spare key; the key may need to be programmed.

B1601 Incorrect key transponder signal Immobiliser High severity

The key chip has been recognised, but the code does not match.

Symptoms

  • The engine won’t start with a particular key

Common causes

  • Key not programmed or damaged
  • interference from other keys

Estimated repair cost40–150 €

What to do: Key reprogramming; check that there are no other keys or key rings on the key ring that might interfere.

B2290 Error in the Occupant Classification System (OCS) SRS sensors High severity

The seat load sensor fails to detect a passenger — the airbag may be deactivated when it should not be.

Symptoms

  • The passenger airbag indicator light is on
  • the airbag is deactivated

Common causes

  • Faulty seat load sensor
  • calibration required

Estimated repair cost80–400 €

What to do: OCS calibration / carpet sensor check at the service centre.

B2292 Fault in the belt tensioner circuit Seat belts High severity

The problem with the pyrotechnic tensioner circuit.

Symptoms

  • The SRS warning light is on
  • the seatbelt indicator is showing an error

Common causes

  • Fault in the seatbelt microswitch
  • disconnected connector under the seat
  • damaged wires

Estimated repair cost30–150 €

What to do: SRS — for the service centre.

B2425 Break in the driver’s seat heating circuit Comfort Low severity

The seat heating isn't working — the heating element is broken.

Symptoms

  • The driver's seat is not heating up

Common causes

  • Broken heating element
  • disconnected connector under the seat
  • faulty switch

Estimated repair cost40–200 €

What to do: Check the connection under the seat; the heating mat is the part that needs replacing most often.

B2513 Fault in the fan motor circuit Climate control Medium severity

The cabin fan is not working or is not operating at all speeds.

Symptoms

  • The cabin fan is not working or is only operating at one speed

Common causes

  • Faulty resistor or control module
  • worn-out motor

Estimated repair cost30–200 €

What to do: Check the fan resistor/control module and the motor itself.

B2607 Fault in the immobiliser lock circuit Immobiliser High severity

Fault in the immobiliser control circuit — ignition may be blocked.

Symptoms

  • The engine won’t start
  • the immobiliser warning light is on

Common causes

  • Fault in the immobiliser control circuit
  • misalignment of modules

Estimated repair cost60–300 €

What to do: Immobiliser diagnostics at the garage.

B2800 Steering column lock malfunction Steering column High severity

Fault with the electric steering lock — the car may not start.

Symptoms

  • The steering wheel won't turn or lock
  • the engine won't start

Common causes

  • Worn-out electric lock mechanism
  • control fault

Estimated repair cost150–600 €

What to do: The lock module is replaced frequently; reprogramming sometimes helps.

B2900 VIN discrepancy between control units Control units Medium severity

A replaced or reprogrammed module has a different VIN.

Symptoms

  • Warning lights are on
  • some functions are disabled

Common causes

  • An engine from another car has been fitted
  • the VIN does not match

Estimated repair cost30–200 €

What to do: Engine block coding specific to the car (this is normal after a replacement — it needs to be adjusted).

B3045 Security system signal is too low Immobiliser High severity

Problem with the security/immobiliser signal level.

Symptoms

  • It won’t start, or it doesn’t start straight away

Common causes

  • Weak key recognition signal
  • fault with the antenna or cables

Estimated repair cost40–200 €

What to do: Check the antenna ring around the lock and the wiring harness.

C0035 Fault in the left front wheel speed sensor circuit ABS / wheel sensors High severity

The ABS is not receiving wheel speed data — the ABS/ESP warning lights come on and the stability control systems are deactivated.

Symptoms

  • The ABS and ESP warning lights are on
  • the ABS is not working
  • the steering may become stiff

Common causes

  • Faulty wheel speed sensor
  • broken cable
  • contaminated or damaged toothed ring

Estimated repair cost30–120 €

What to do: Check the sensor, its cable and the toothed ring (the cable is often broken near the bend).

C0040 Fault in the right front wheel speed sensor circuit ABS / wheel sensors High severity

Like C0035, the next wheel.

Symptoms

  • The ABS and ESP warning lights are on
  • the ABS is not working
  • the steering may become stiff

Common causes

  • Faulty wheel speed sensor
  • broken cable
  • contaminated or damaged toothed ring

Estimated repair cost30–120 €

What to do: See C0035.

C0045 Fault in the left rear wheel speed sensor circuit ABS / wheel sensors High severity

Same as C0035, rear wheel.

Symptoms

  • The ABS and ESP warning lights are on
  • the ABS is not working
  • the steering may become stiff

Common causes

  • Faulty wheel speed sensor
  • broken cable
  • dirty or damaged toothed ring

Estimated repair cost30–120 €

What to do: See C0035.

C0050 Fault in the right rear wheel speed sensor circuit ABS / wheel sensors High severity

Same as C0035, rear wheel.

Symptoms

  • The ABS and ESP warning lights are on
  • the ABS is not working
  • the steering may become stiff

Common causes

  • Faulty wheel speed sensor
  • broken cable
  • contaminated or damaged toothed ring

Estimated repair cost30–120 €

What to do: See C0035.

C0110 Fault in the ABS pump motor circuit ABS hydraulics High severity

The ABS hydraulic unit pump is not working — the ABS function is disabled.

Symptoms

  • The ABS warning light is on
  • the ABS is not working
  • braking distance is longer on slippery surfaces

Common causes

  • Faulty ABS pump motor
  • blown fuse
  • poor ground connection

Estimated repair cost100–600 €

What to do: Check the pump’s power supply and connections; the ABS module is often repaired.

C0121 Fault in the ABS valve relay circuit ABS hydraulics High severity

Problem with the power supply to the valves in the hydraulic unit.

Symptoms

  • The ABS and ESP warning lights are on
  • the systems are deactivated

Common causes

  • Fault in the ABS unit’s internal relay
  • power supply issue

Estimated repair cost100–600 €

What to do: ABS module diagnostics; check the fuses.

C0161 Fault in the brake pedal switch signal Brakes Medium severity

The ABS/ESP system is not receiving the correct brake pedal signal.

Symptoms

  • The ESP is not working
  • the brake lights are either not coming on or are constantly on

Common causes

  • Worn pedal switch
  • misaligned position

Estimated repair cost15–80 €

What to do: Check / replace the brake light switch and adjust it.

C0196 Yaw sensor signal interference ESP sensors High severity

The stability control system is not receiving the correct signal regarding the car’s rotation.

Symptoms

  • The ESP warning light is on
  • the system activates unnecessarily or is not working

Common causes

  • Sensor fault
  • calibration required following repair

Estimated repair cost60–400 €

What to do: Calibration or replacement of the sensor; following work on the steering system — calibration of the steering angle.

C0265 Fault in the ABS/EBCM module relay ABS hydraulics High severity

A problem with the internal relays in the ABS control unit is a common fault with GM/Opel vehicles.

Symptoms

  • The ABS warning light is on
  • the ABS and ESP are not working

Common causes

  • Fault in the ABS module’s internal relay (a common problem with GM / Opel vehicles)

Estimated repair cost100–500 €

What to do: Repair or replacement of the ABS module.

C0460 Steering angle sensor signal fault Steering mechanism High severity

The ESP no longer knows the position of the steering wheel — stability control is deactivated.

Symptoms

  • The ESP warning light is on
  • the steering wheel position is displayed incorrectly

Common causes

  • Calibration not carried out after alignment
  • sensor fault
  • damage to the coiled cable

Estimated repair cost20–300 €

What to do: Carry out the steering angle sensor calibration (required after wheel alignment).

C1095 Fault with the ABS hydraulic pump ABS hydraulics High severity

A problem with the pump circuit or pressure.

Symptoms

  • The ABS warning light is on
  • the systems are deactivated

Common causes

  • Pump fault
  • pressure sensor fault
  • in the air system

Estimated repair cost100–600 €

What to do: ABS module diagnostics at the garage.

C1201 An engine control fault disables the ABS/ESP ABS / ESP Medium severity

Toyota/Lexus: an engine fault automatically disables the stability control systems — address the P codes first.

Symptoms

  • The ‘Check Engine’, ABS and ESP warning lights are all on at the same time

Common causes

  • Any engine control fault (Toyota/Lexus-specific)

Estimated repair cost0 €

What to do: Scan and clear the engine fault codes — this code will disappear as well.

C1300 Internal fault in the brake control unit ABS / ESP High severity

ESP/ABS module self-test fault.

Symptoms

  • The ABS and ESP warning lights are on

Common causes

  • Internal fault in the ESP unit
  • power supply or ground issues

Estimated repair cost100–600 €

What to do: Block diagnostics; check the power supply and ground connections.

U0001 Fault on the high-speed CAN bus CAN bus High severity

A communication fault on the main CAN bus — this can cause a lot of errors across all modules.

Symptoms

  • Several warning lights are illuminated at the same time
  • several systems are not functioning
  • the modules cannot be accessed for diagnostics

Common causes

  • Damaged CAN cables or connectors
  • moisture in the connectors
  • a faulty control unit is causing a fault on the bus

Estimated repair cost30–300 €

What to do: Check the CAN cables and connectors; often, a single ‘noisy’ module is to blame — disconnect them one by one.

U0100 There is no connection to the engine control module (ECM) The connection between blocks High severity

The other blocks are no longer receiving data from the engine block.

Symptoms

  • Won’t start
  • revs not displayed
  • numerous errors in other modules

Common causes

  • ECU power supply or ground fault
  • blown fuse
  • CAN fault

Estimated repair cost30–400 €

What to do: Check the ECU power supply, fuses, ground connections and CAN connectors.

U0101 No connection to the transmission control module (TCM) The connection between blocks High severity

Loss of communication with the transmission control unit — the gearbox may operate in emergency mode.

Symptoms

  • Crash mode
  • impacts
  • gear not displayed

Common causes

  • TCM power supply fault
  • CAN connection issue

Estimated repair cost30–400 €

What to do: Check the TCM power supply and the CAN circuit.

U0121 No connection to the ABS control unit The connection between blocks High severity

Loss of connection to the ABS — the ABS/ESP warning lights are on.

Symptoms

  • The ABS and ESP warning lights are on

Common causes

  • ABS module power supply
  • CAN connections
  • module fault

Estimated repair cost30–400 €

What to do: ABS module power supply, fuses, CAN connectors.

U0140 There is no connection to the Body Control Module (BCM) The connection between blocks Medium severity

Loss of connection with the body module — lights, windows and central locking may malfunction.

Symptoms

  • The lights, windows or central locking are not working
  • various faults

Common causes

  • BCM power supply fault
  • CAN fault
  • moisture in the unit

Estimated repair cost30–400 €

What to do: BCM power supply and CAN check.

U0155 No connection to the instrument panel The connection between blocks Medium severity

The display is not receiving any data — it is not showing revs, speed or other readings.

Symptoms

  • The control panel is not working or has switched off

Common causes

  • Panel power supply
  • CAN connections
  • panel fault

Estimated repair cost30–400 €

What to do: Panel power supply and CAN connections.

U0300 Incompatible software versions of the control units Software Medium severity

Following a block change or update, the versions do not match.

Symptoms

  • Various errors following a block change or update

Common causes

  • Incompatible software versions
  • encoding not performed

Estimated repair cost30–200 €

What to do: Block programming/coding at the agent’s premises or using suitable equipment.

U0401 Unreliable data received from the ECM Data reliability Medium severity

Other blocks receive conflicting data from the engine block.

Symptoms

  • Emergency mode
  • power limitation

Common causes

  • Engine block faults
  • CAN noise
  • sensor discrepancies

Estimated repair cost20–300 €

What to do: First of all, troubleshoot the engine block codes; check the CAN signal quality.

U1000 Manufacturer’s CAN communication error CAN bus Medium severity

General manufacturer's network error — the meaning depends on the brand.

Symptoms

  • Several warning lights are illuminated at the same time
  • several systems are not functioning
  • the modules cannot be accessed for diagnostics

Common causes

  • Damaged CAN cables or connectors
  • moisture in the connectors
  • a faulty control unit is causing a fault on the bus

Estimated repair cost30–300 €

What to do: Scan the codes from all the blocks — look for a specific block that is not responding.

What do the letters mean?

OBD2 fault codes always start with one of four letters — it tells you which system is affected: P — powertrain, B — body, C — chassis, U — network communication between modules. The second character “0” means a standard (generic) code, “1” — manufacturer-specific.

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