This section lists 379 fault codes across 18 system groups: 129 critical, 199 warning and 51 info severity. The classification is CarCoding’s own.
Fault codes by system group
- ABS and Brakes43 codes The ABS/ESP module continuously watches four wheel speed sensors and the valves inside the hydraulic unit; codes in this group usually mean one wheel speed signal disagrees with the others, or a valve or pump circuit could not be driven as expected.
- Air-Fuel Mixture25 codes How much air the engine takes in on each cycle is the basis for injection timing; codes in this group arise from a mismatch between the measured air and the air the control unit expected.
- Airbag (SRS)15 codes The SRS module monitors the circuit resistance of airbag and seat belt pretensioner squibs, the crash sensors and the belt switches; when a measured resistance leaves its narrow window a code is stored and the SRS lamp comes on.
- Body and Comfort11 codes Body-side codes are stored when an output does not draw the expected current, a switch reports an impossible position, or comfort modules cannot reach each other.
- Chassis19 codes Chassis codes rest on sensors that measure vehicle motion; a sensor losing its zero point or contradicting the others is the typical source of codes in this group.
- Cooling System9 codes For the control unit, coolant temperature is not a single value but a time-temperature curve; codes in this group arise when the temperature does not follow the expected curve.
- Electrical and Electronics30 codes This group collects codes about the modules themselves and the supply and ground infrastructure rather than a specific mechanical system; they are usually on the cause side, not the effect side.
- Emissions and Exhaust54 codes Most emissions codes are comparisons rather than direct measurements; the control unit decides whether a system is still doing its job by watching how sensors behave relative to each other.
- Engine1 codes General engine codes usually report an outcome rather than a cause: the control unit saw that expected behaviour did not happen but could not narrow the blame to one circuit.
- Fuel System34 codes The most misleading thing about fuel system codes is that, despite the name, the cause is often on the air side: a vacuum leak looks like a fuel shortage from the control unit’s point of view.
- Ignition System27 codes There is no dedicated sensor that sees a misfire: the control unit counts stumbles in the instantaneous speed of the crankshaft. As a result, a faulty crank signal can make the module “see” misfires that never happened.
- Lubrication System6 codes In modern engines oil pressure is not only lubrication but also an actuator supply; that is why lubrication problems often show up first as VVT and timing codes.
- Network and CAN Bus27 codes Codes starting with U describe a silence rather than a fault: one module did not receive a message it expected from another. That does not mean the other module is broken.
- Sensors12 codes The key distinction in sensor codes is between “circuit” and “performance”: the first reports an electrical certainty, the second says the signal is electrically valid but physically wrong.
- Timing5 codes Timing codes are correlation codes: the angular difference between the crankshaft and camshaft signals has left its expected window.
- Transmission36 codes Transmission codes can report an electrical solenoid fault or a mismatch between input and output speed (slip); slip codes can come from mechanical wear just as easily as from degraded fluid.
- Turbo and Boost Pressure6 codes Boost codes can only occur under load, so the vehicle may show no symptom at idle; engine load and rpm in the freeze frame are especially decisive in this group.
- VVT and Valvetrain19 codes The force that rotates a VVT system is engine oil pressure; that is why most codes in this group are not electrical but oil related.
Fault codes by make
Manufacturer-specific codes (P1, C1, B1, U1) differ from make to make; the same number can indicate a different fault elsewhere. That is why each make has its own page.
- BMW46 codes BMW-specific fault codes: manufacturer codes from DME engine management, DSC stability control and FRM body electronics.
- VAG24 codes Manufacturer-specific fault codes shared across Volkswagen, Audi, Seat, Skoda and Porsche.
- Mercedes-Benz18 codes Mercedes-Benz-specific fault codes: engine management, ESP, SAM body modules and CAN-C communication.
- Toyota8 codes Manufacturer-specific fault codes shared across Toyota and Lexus.
- Ford7 codes Manufacturer-specific fault codes for Ford.
One example from each system group
The codes below are one example per group (the lowest code number). They are picked by database order, not by search volume.
Wondering which module stores the code? ECU modules in your vehicle.
Read fault codes on your own vehicle
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Data source: the CarCoding fault code database. Code definitions follow the SAE J2012 standard; manufacturers may use different wording for their own codes. Everything on this page is generated from the code-specific database records.