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Ignition & Misfire Trouble Codes: List & Fixes

P03xx codes cover misfires and the sensors the engine needs to time ignition. P0300 means random or multiple misfires; P0301 to P0312 name the cylinder that is misfiring; crankshaft and camshaft position sensor codes also sit in this range. On coil-on-plug engines, swapping the coil from the misfiring cylinder with a neighboring one and seeing whether the misfire follows is a quick, cheap first test. If the check engine light is flashing, reduce load and get the car checked promptly to protect the catalytic converter.

66Codes
3.0Average severity
15%High or critical
12%DIY-friendly
Severity distributionSeverity distribution

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P0302 Powertrain Cylinder 2 keeps misfiring. On inline engines it's a middle cylinder, so rule out coolant… Moderate P0301 Powertrain Cylinder 1 is repeatedly failing to fire. The cause is almost always its coil, plug, injector… Moderate P0304 Powertrain Cylinder 4 is misfiring. Its end or rear position makes water, oil and intake leaks common… Moderate P0300 Powertrain The engine computer sees misfires that jump between cylinders or hit several cylinders at once. High P0316 Powertrain The engine misfired right after starting, when the catalytic converter is cold and emissions… Low P0320 Powertrain The computer lost the engine speed (rpm) signal. The engine can stall suddenly or refuse… High

All codes (66)

All Severity 3+ Severity 4+
P1381 Chevrolet · Powertrain A misfire was detected while the PCM had lost contact with the ABS module that supplies… Moderate P1391 Jeep · Powertrain The PCM keeps briefly losing the cam or crank position signal, which can make your Jeep stumble… Moderate P1399 Honda · Powertrain An older Honda's PCM counted misfires that jump between cylinders instead of staying in one. Moderate P3400 Powertrain Cylinder shut-off on bank 1 (AFM, DFM, MDS or VCM) isn't doing what the engine computer… Moderate P3401 Powertrain The engine computer sees a broken or open circuit to the solenoid that shuts off cylinder 1. Low P3497 Honda · Powertrain Honda's Variable Cylinder Management on the front cylinder bank didn't behave the way the PCM… Moderate

Subsystems

Fuel & Air Metering 193Emission Controls 97Speed & Idle Control 57Transmission 57ECU & Outputs 54Module Communication 43Brakes, ABS & Chassis 36Body Systems 31Hybrid / EV 14