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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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P0300 Powertrain The engine computer sees misfires that jump between cylinders or hit several cylinders at once. High P0302 Powertrain Cylinder 2 keeps misfiring. On inline engines it's a middle cylinder, so rule out coolant… Moderate P0303 Powertrain Cylinder 3 is misfiring. Check whether it misses at idle or under load before you blame… Moderate P0304 Powertrain Cylinder 4 is misfiring. Its end or rear position makes water, oil and intake leaks common… Moderate P0325 Powertrain The computer isn't getting a usable signal from knock sensor 1, so it pulls timing to protect… Low P0335 Powertrain The engine computer lost the crankshaft position signal. Expect stalling or a crank-no-start. 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