Fault codes explained
The codes owners actually meet, in plain English: what each means, how serious it is, and what to check first.
A fault code is five characters. The letter says which system set it — Powertrain,
Chassis, Body or U for the network between
modules. A 0 or 2 next means a generic code that means the same on every car;
a 1 or 3 means the manufacturer defined it. The third character narrows it to
an area of the car, and the last two are the fault itself.
Powertrain
Engine, fuel, ignition, emissions and gearbox — the P codes behind most check engine lights.
- P0010 Camshaft position actuator circuit (bank 1) Needs attention
- P0011 Camshaft position — timing over-advanced (bank 1) Needs attention
- P0016 Crankshaft/camshaft position correlation (bank 1) Urgent
- P0030 Oxygen sensor heater circuit (bank 1, sensor 1) Advisory
- P0071 Ambient air temperature sensor range/performance Advisory
- P0100 Mass air flow circuit Needs attention
- P0101 Mass air flow circuit range/performance Needs attention
- P0102 Mass air flow circuit low input Needs attention
- P0113 Intake air temperature circuit high input Advisory
- P0116 Coolant temperature circuit range/performance Needs attention
- P0117 Coolant temperature circuit low input Needs attention
- P0118 Coolant temperature circuit high input Urgent
- P0121 Throttle position sensor range/performance Needs attention
- P0128 Coolant thermostat below regulating temperature Advisory
- P0130 Oxygen sensor circuit (bank 1, sensor 1) Needs attention
- P0133 Oxygen sensor slow response (bank 1, sensor 1) Needs attention
- P0135 Oxygen sensor heater circuit (bank 1, sensor 1) Advisory
- P0171 Fuel system too lean (bank 1) Needs attention
- P0172 Fuel system too rich (bank 1) Needs attention
- P0174 Fuel system too lean (bank 2) Needs attention
- P0175 Fuel system too rich (bank 2) Needs attention
- P0190 Fuel rail pressure sensor circuit Needs attention
- P0201 Injector circuit — cylinder 1 Needs attention
- P0217 Engine over-temperature condition Urgent
- P0300 Random/multiple cylinder misfire Urgent
- P0301 Cylinder 1 misfire Urgent
- P0302 Cylinder 2 misfire Urgent
- P0303 Cylinder 3 misfire Urgent
- P0304 Cylinder 4 misfire Urgent
- P0305 Cylinder 5 misfire Urgent
- P0306 Cylinder 6 misfire Urgent
- P0327 Knock sensor circuit low (bank 1) Needs attention
- P0335 Crankshaft position sensor circuit Urgent
- P0340 Camshaft position sensor circuit Needs attention
- P0401 Exhaust gas recirculation flow insufficient Advisory
- P0402 Exhaust gas recirculation flow excessive Advisory
- P0420 Catalyst system efficiency below threshold (bank 1) Needs attention
- P0430 Catalyst system efficiency below threshold (bank 2) Needs attention
- P0440 Evaporative emission system Advisory
- P0442 Evaporative emission system small leak Advisory
- P0455 Evaporative emission system large leak Advisory
- P0456 Evaporative emission system very small leak Advisory
- P0500 Vehicle speed sensor Needs attention
- P0505 Idle air control system Needs attention
- P0520 Engine oil pressure sensor circuit Urgent
- P0562 System voltage low Needs attention
- P0563 System voltage high Needs attention
- P0601 Control module memory checksum error Urgent
- P0620 Generator control circuit Needs attention
- P0700 Transmission control system Needs attention
- P0715 Input/turbine speed sensor circuit Needs attention
- P0740 Torque converter clutch circuit Needs attention
- P2002 Diesel particulate filter efficiency below threshold Needs attention
- P2096 Post-catalyst fuel trim system too lean (bank 1) Needs attention
- P2463 Diesel particulate filter — soot accumulation Needs attention
Chassis
Brakes, steering and suspension.
- C0035 Left front wheel speed sensor circuit Needs attention
Body
Comfort, lighting, locking and restraints.
- B1000 Control module fault Needs attention
Network
The control modules talking to each other.
- U0100 Lost communication with engine control module Urgent
- U0101 Lost communication with transmission control module Urgent
- U0121 Lost communication with ABS control module Urgent
Read and clear any code from your iPhone with OBDTrip
Plug a Bluetooth OBD-II adapter into the car and OBDTrip reads every stored, pending and permanent code, explains each one in plain English like this, shows what the engine was doing when it was set, and clears the check engine light once the fault is fixed. It keeps a history of when each code comes back, and records every drive on its own from then on.
Needs a Bluetooth Low Energy adapter such as the Vgate iCar Pro — which adapters work with iPhone. Reading and clearing codes is part of an OBDTrip subscription.