Powertrain codes
Engine, fuel, ignition, emissions, transmission and hybrid/EV drive. Most check-engine lights are P codes.
Powertrain code groups
Hybrid & EV
1,528 codesHigh-voltage battery, drive motors, inverters, chargers and the cooling loops that serve them. Most need a shop with high-voltage training.
Transmission
1,164 codesAutomatic, dual-clutch and manual transmission controls: shift and pressure solenoids, speed sensors, range sensors, clutches and fluid temperature.
Misfire & ignition
444 codesCylinder misfires, ignition coils, spark and glow plugs, knock sensors and ion-sense circuits.
O2 sensors
200 codesUpstream and downstream oxygen sensors, wideband air-fuel sensors and their heater circuits.
Timing, cam & crank
442 codesCamshaft and crankshaft position sensors, variable valve timing, valve lift and cylinder deactivation.
Emissions
995 codesCatalytic converters, the EVAP fuel-vapor system, EGR, secondary air, diesel aftertreatment (DPF, SCR/DEF, NOx) and crankcase ventilation.
Cooling
343 codesCoolant temperature sensors, thermostats, cooling fans, coolant pumps and over-temperature protection.
Fuel & air
1,571 codesLean and rich conditions, fuel trim, injectors, fuel pressure, MAF and MAP sensors, throttle, intake air temperature and turbo/supercharger boost.
Speed, idle & cruise
281 codesVehicle speed sensors, idle air control, cruise control inputs, brake switches and torque-management signals.
Computer & electrical
287 codesECM/PCM internal faults, sensor reference voltages, charging system, starter and power relays.
Other powertrain
74 codesPowertrain codes outside the groups above, including newer SAE blocks that mix several subsystems.
Common P codes
- P0420Catalyst System Efficiency Below Threshold (Bank 1)Often: catalyst aged or contaminatedModerate$190–$625 labor est.
- P0300Random/Multiple Cylinder Misfire DetectedOften: vacuum leak affecting all cylindersUrgent$65–$750 labor est.
- P0171System Too Lean (Bank 1)Often: MAF sensor contaminated, under-readingModerate$65–$500 labor est.
- P0455Evaporative Emission System Leak Detected (Large Leak)Often: EVAP hose disconnectedLow$15–$315 labor est.
- P0442Evaporative Emission System Leak Detected (Small Leak)Often: fuel cap loose, missing, or worn sealLow$15–$250 labor est.
- P0128Coolant Thermostat Below Regulating TemperatureOften: thermostat stuck openModerate$90–$375 labor est.
- P0401Exhaust Gas Recirculation Flow Insufficient DetectedOften: intake EGR passages blocked with carbonModerate$125–$625 labor est.
- P0174System Too Lean (Bank 2)Often: MAF sensor contaminatedModerate$65–$500 labor est.