Fault codes
479 standardised codes across 30 functional groups and 29 marques. Each page gives what the code means, what it usually turns up alongside, and how often we see it in real diagnostics.
The codes we see most
- P0299 Turbocharger underboost condition 75 diagnostics · 31 workshops
- P0171 System too lean, bank 1 60 diagnostics · 36 workshops
- P0300 Random or multiple cylinder misfire detected 44 diagnostics · 37 workshops
- P2002 Diesel particulate filter efficiency below threshold, bank 1 36 diagnostics · 19 workshops
- P0420 Catalyst system efficiency below threshold, bank 1 35 diagnostics · 24 workshops
- P20EE SCR NOx catalyst efficiency below threshold, bank 1 27 diagnostics · 13 workshops
- P0011 A camshaft position timing over-advanced or system performance, bank 1 24 diagnostics · 15 workshops
- P0128 Coolant thermostat, coolant below regulating temperature 23 diagnostics · 23 workshops
- P0303 Cylinder 3 misfire detected 22 diagnostics · 11 workshops
- P0301 Cylinder 1 misfire detected 22 diagnostics · 10 workshops
- P0017 Crankshaft/camshaft position correlation, bank 1 sensor B 22 diagnostics · 8 workshops
- P0087 Fuel rail/system pressure too low 20 diagnostics · 12 workshops
- P0401 Exhaust gas recirculation flow insufficient 19 diagnostics · 10 workshops
- P0101 Mass or volume air flow circuit range/performance 18 diagnostics · 12 workshops
- P2463 Diesel particulate filter restriction, soot accumulation 18 diagnostics · 10 workshops
- P0562 System voltage low 17 diagnostics · 4 workshops
- P0201 Injector circuit open, cylinder 1 15 diagnostics · 6 workshops
- P2563 Turbocharger boost control position sensor circuit range/performance 14 diagnostics · 9 workshops
- P0090 Fuel pressure regulator 1 control circuit 14 diagnostics · 5 workshops
- P0016 Crankshaft/camshaft position correlation, bank 1 sensor A 13 diagnostics · 7 workshops
- P0234 Turbocharger overboost condition 13 diagnostics · 8 workshops
- P0204 Injector circuit open, cylinder 4 13 diagnostics · 5 workshops
- P0202 Injector circuit open, cylinder 2 13 diagnostics · 5 workshops
- P0193 Fuel rail pressure sensor circuit high 13 diagnostics · 5 workshops
By what part of the vehicle
- Turbo and boost control 26 codes
- Not yet classified 79 codes
- Bus communication 49 codes
- Valve timing and camshaft 17 codes
- Fuel pressure and delivery 23 codes
- Diesel particulate filter 16 codes
- Misfire 8 codes
- Air intake and MAF/MAP 20 codes
- Fuel trim: lean or rich 9 codes
- Transmission 37 codes
- Lambda and O2 sensors 21 codes
- SCR and AdBlue 15 codes
- EGR 8 codes
- Injectors 10 codes
- Cooling and thermostat 10 codes
- Catalytic converter 5 codes
- EVAP and fuel tank 15 codes
- Throttle and pedal 15 codes
- ECU internal and software 13 codes
- Body, manufacturer-specific 13 codes
- Glow plugs and preheat 9 codes
- Hybrid and EV propulsion 9 codes
- Idle and speed control 11 codes
- Charging and system voltage 6 codes
- ABS, brakes and stability 9 codes
- Exhaust pressure and temperature 7 codes
- Engine oil and lubrication 6 codes
- Chassis, manufacturer-specific 5 codes
- Ignition and knock sensing 5 codes
- Airbags and restraints 3 codes
By marque
Where the manufacturer-specific codes live. They get no page of their own because the same code means different things on different marques, but scoped to one marque the question becomes answerable.
- Volkswagen · 227
- Volvo · 199
- Mercedes-Benz · 176
- Audi · 128
- Ford · 118
- Saab · 93
- Peugeot · 96
- Toyota · 58
- BMW · 39
- Skoda · 56
- Nissan · 63
- Land Rover · 62
- Ford (eu) · 65
- Citroen · 91
- KIA · 44
- Opel · 57
- Renault · 45
- Hyundai · 28
- Chevrolet · 25
- Fiat · 29
- Porsche · 25
- Mazda · 18
- Honda · 22
- Seat · 12
- Jeep · 14
- Jaguar · 11
- Subaru · 13
- Mitsubishi · 8
- Vauxhall · 13
What is deliberately not here
Manufacturer-specific codes have no page of their own. The second character of a code says whether it is standardised, and a manufacturer-specific one genuinely means different things on different marques. A single page about such a code would be wrong more often than right, so they are listed on the group pages as codes we have seen, with no meaning attached, and on the marque hubs above where they can finally be read in context.
Codes we have met once and cannot describe are also left out. There is nothing a page could say about them that the group page does not say better, and a page that exists only to exist helps nobody.
Figures on these pages are as of 2026-10-06, measured across diagnostics run through Wrenchlane by independent workshops.
FAQ
Frequently asked questions
How do I run a diagnosis?
Select the vehicle on Start, click the Diagnostic card and choose New diagnostic. Fill in the description, the error codes and the mileage, then click Analyze.
Learn more: Diagnostic (vehicle-first start), Diagnostic form: description, error codes and mileage
Do I have to type the codes from my scan tool?
No. Click the camera button next to Error codes and take or choose a photo (JPEG or PNG) of the scan tool's screen; WrenchLane reads the codes and their descriptions into the form. You can also speak them with the microphone.
Learn more: OBD reader photo scan (fault codes from a photo), Voice input for the problem description
Are the public fault code pages built from my diagnostics?
They are built from anonymised, aggregated diagnostics run in WrenchLane; no workshop, customer or vehicle can be identified. Each fault code page shows how often the code was seen across those diagnostics and in how many separate workshops.
Learn more: Fault code pages on wrenchlane.com (fault-code cluster)
Put a code against a real car
Enter the code and the symptoms and get ranked probable causes for that specific vehicle, with the checks in the order worth doing them. Free account, no card.
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