What does your fault code mean?
Type it here. We tell you what the car detected, whether you can keep driving and what to check first.
Tap the boxes and type your code. These are only examples.
- LetterPowertrain: engine and transmission
- 2ndGeneric code: same on every make
- 3rdEmissions
- End20
Which warning light is on?
Tap the one you see on your dashboard.
Engine: Check it soon. If it flashes, stop when safe
The control module detected an engine or emissions fault. If it stays on with no symptoms, drive gently to a shop. A flashing light usually means misfires that can damage the catalytic converter.
Related codes
Oil: Stop and switch off the engine
Oil pressure may be low. Stop somewhere safe, switch off the engine and check the level. Driving on can destroy the engine.
Related codes
Temperature: Stop and let it cool
The engine may be overheating. Stop somewhere safe and switch it off. Do not open the cooling system while hot, as it can burn you.
Related codes
Battery: Head to a shop, avoiding engine stops if you can
The battery is probably not charging. Turn off what you do not need and drive straight to a shop, because the car may run out of power.
Related codes
ABS: Drive with care
Normal braking usually still works, but without ABS. Leave more distance and go to a shop. If the pedal feels different or the red brake light comes on, do not continue.
Related codes
Airbag: Get it repaired as soon as possible
The airbag or pretensioners may not work in a crash. Do not test these circuits with a multimeter: leave the repair to a professional.
Related codes
Diesel filter: Deal with it soon
The particulate filter is filling up. If it is only a warning, a drive on a fast road can help it regenerate. If the car loses power, go to a shop.
Related codes
Glow plugs: Check it soon
On diesels, it shows preheating. On for a few seconds at startup is normal. If it flashes while driving, there is a fault worth reading with a scanner.
Related codes
AdBlue: Do not put it off
AdBlue is low or the system has a fault. Top up if it is low. If a countdown appears, the car may not restart when it reaches zero.
Related codes
Symbols and colors vary by car. Always check the manual.
What is your car doing?
Pick what you notice and we will tell you where to start.
This often points to the turbo, fuel, air intake or particulate filter. If the car enters limp mode, avoid fast roads.
This is typical of misfires or mixture problems. If the light flashes, slow down and stop when safe.
Check air leaks, the throttle and the EGR valve first.
Start with the battery. Then check the crankshaft and camshaft sensors, fuel pressure and, on diesels, the glow plugs.
If it is heavy, blue or coming from the engine bay, stop and check before going on. Black smoke usually means too much fuel.
If the temperature rises, stop somewhere safe and switch off the engine. Do not open the system while hot.
An engine that does not reach temperature, a wrong mixture or an oxygen sensor can raise consumption.
If the smell is strong, find the leak before going on, ventilate and do not smoke nearby. Start with the fuel cap.
Check the transmission fluid level and condition. If it slips or stays in one gear, drive slowly or call a tow truck.
Recently viewed
Common codes
- P0420Catalyst System Efficiency Below Threshold Bank 1
- P0171System Too Lean Bank 1
- P0401EGR A Flow Insufficient Detected
- P0101Mass or Volume Air Flow Sensor A Circuit Range/Performance
- P0128Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
- P0700Transmission Control System (MIL Request)
- P2463Diesel Particulate Filter Restriction - Soot Accumulation (Bank 1)
- P0172System Too Rich Bank 1
- P0300Random/Multiple Cylinder Misfire Detected
- P0299Turbocharger/Supercharger A Underboost Condition
- P2002Diesel Particulate Filter Efficiency Below Threshold (Bank 1)
- P0340Camshaft Position Sensor A Circuit Bank 1 or Single Sensor
- P0442EVAP System Leak Detected (small leak)
- P0087Fuel Rail/System Pressure - Too Low
- P0335Crankshaft Position Sensor A Circuit
- U0100Lost Communication with ECM/PCM "A"
Explore the codes
We could not find that brand. Generic codes work the same on any car.
- Air intake and turboMAF, MAP, throttle, turbo and intake air temperature.
- Fuel and mixtureInjectors, pressure, pump and rich or lean mixture.
- Ignition and engineMisfires, coils, glow plugs, crankshaft and camshaft.
- EmissionsCatalyst, oxygen sensors, EGR, DPF, AdBlue and EVAP.
- CoolingEngine temperature, thermostat and fan.
- LubricationOil pressure, temperature and level.
- Idle and speedIdle, speed sensor and cruise control.
- Electronics and chargingControl modules, battery, alternator and reference voltages.
- TransmissionSolenoids, sensors and torque converter clutch.
- Brakes and chassisC codes: ABS, stability, steering and suspension.
- Body and airbagB codes: airbag, comfort, lights and cluster.
- Communication networkU codes: lost communication between modules.
- Hybrid and electricHigh-voltage battery, inverter and electric motor.
- Other systemsCodes outside the main families.
- B00xx152 codes
- B01xx75 codes
- B02xx32 codes
- B03xx14 codes
- B04xx8 codes
- B05xx17 codes
- B06xx3 codes
- B07xx2 codes
- B08xx12 codes
- B09xx8 codes
- C00xx116 codes
- C01xx21 codes
- C02xx36 codes
- C03xx20 codes
- C04xx15 codes
- C05xx256 codes
- C06xx115 codes
- C07xx13 codes
- C08xx18 codes
- C09xx16 codes
- P00xx255 codes
- P01xx256 codes
- P02xx256 codes
- P03xx253 codes
- P04xx256 codes
- P05xx256 codes
- P06xx256 codes
- P07xx256 codes
- P08xx234 codes
- P09xx147 codes
- P0Axx256 codes
- P0Bxx256 codes
- P0Cxx256 codes
- P0Dxx256 codes
- P0Exx255 codes
- P0Fxx1 codes
- P20xx256 codes
- P21xx256 codes
- P22xx256 codes
- P23xx256 codes
- P24xx256 codes
- P25xx256 codes
- P26xx256 codes
- P27xx242 codes
- P28xx247 codes
- P2Axx256 codes
- P2Bxx256 codes
- P2Cxx256 codes
- P2Dxx254 codes
- P2Exx192 codes
- P34xx155 codes
- U00xx116 codes
- U01xx182 codes
- U02xx174 codes
- U03xx80 codes
- U04xx181 codes
- U05xx161 codes
- U06xx160 codes
- U09xx1 codes
- U30xx55 codes
- U35xx119 codes
Guides to understand your fault
- Check engine light on: what to do and when to stopWhat a steady or flashing check engine light means, when you can keep driving, and how to find the cause with an OBD reader.
- How to read fault codes with an OBD2 readerWhere the OBD2 port is, which reader you need, and how to read and interpret fault codes step by step.
- How to interpret an OBD code: what each character meansAn OBD code has one letter and four characters. Learn what each one indicates and the difference between generic and manufacturer codes.
- Clearing fault codes: when it helps and when it is a bad ideaWhat happens when you clear an OBD code, why it may come back, and what you should write down before doing it.
- Limp mode: why your car suddenly loses powerWhat limp mode is, which faults trigger it, and what to do if your car loses power while you are driving.
How to use this information
A code tells you what the control module detected, not which part to replace. P0171, for example, can come from an air leak, a mass air flow sensor or low fuel pressure, so each page starts with the simplest checks.
Generic codes such as P0xxx and P2xxx mean the same on every make. Brand-specific codes vary by make, model and year.