Loss of power: Codes, Causes & Fixes

P0174 Powertrain The cylinder bank without cylinder 1 is running lean even with the maximum fuel correction… Moderate P0420 Powertrain The bank 1 catalytic converter no longer stores enough oxygen to clean the exhaust properly. Low P0101 Powertrain The MAF sensor's airflow reading doesn't match what the engine computer expects… Low P0171 Powertrain The engine computer is adding the maximum extra fuel it's allowed on bank 1 and still sees… Moderate P0299 Powertrain The turbo or supercharger isn't building the boost pressure the engine computer is asking for. Moderate 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 P0305 Powertrain Cylinder 5 is misfiring. First job: work out which bank it sits on, because that decides what… Moderate P0306 Powertrain Cylinder 6 is misfiring. On an inline-six it's the hot rear cylinder; on GM and Hemi V8s it can… Moderate P0307 Powertrain Cylinder 7 is misfiring. On GM and Hemi V8s it's a cylinder-deactivation cylinder, so check… Moderate P0308 Powertrain Cylinder 8 is misfiring. It's a rear V8 cylinder against the firewall, so its plug is often… Moderate P0321 Powertrain The rpm signal is there but erratic: extra or missing pulses the computer can't trust. Expect… Moderate P0325 Powertrain The computer isn't getting a usable signal from knock sensor 1, so it pulls timing to protect… Low P0326 Powertrain Knock sensor 1 works electrically, but what it hears doesn't match what the computer expects. Low P0327 Powertrain Knock sensor 1's signal is too weak or pulled to ground: usually wiring, water or a loose… Low P0328 Powertrain Knock sensor 1's signal is too strong: a short to voltage, electrical noise or a genuinely… Low P0330 Powertrain The second knock sensor, usually the one for the bank without cylinder 1, has a circuit fault. Low P0332 Powertrain Knock sensor 2 reads too low. On a V engine it's the bank without cylinder 1; on some fours… Low P0336 Powertrain Crank signal present but implausible: damaged teeth, a slipped balancer ring or debris confuse… Moderate P0340 Powertrain The computer lost the camshaft signal on bank 1. Expect long cranking, less power… Moderate P0341 Powertrain The bank 1 cam signal lands at the wrong crank angle, often from a stretched chain or a sticky… Moderate P0342 Powertrain The bank 1 cam sensor signal stays near 0 volts. Often a weak battery, a pinched wire… Moderate P0343 Powertrain The bank 1 cam signal is stuck high: an unlatched connector, broken ground or open wire after… Moderate P0345 Powertrain The cam sensor on bank 2, the side without cylinder 1, has a missing or faulty signal on a V6… Moderate P0346 Powertrain Bank 2's cam signal arrives out of position. On V6/V8s that often means a bank 2 chain, guide… Moderate P0351 Powertrain The engine computer found an electrical fault in coil A, the coil that fires cylinder 1 on most… Moderate P0352 Powertrain Coil B, normally on cylinder 2, has a circuit fault. Where cylinder 2 sits depends… Moderate P0353 Powertrain The circuit for coil C, which fires cylinder 3, failed its electrical check. Wiring is a big… Moderate P0355 Powertrain Coil E, the coil for cylinder 5, has an electrical fault. Only engines with five or more… Moderate P0356 Powertrain The coil F circuit for cylinder 6 failed its check. On inline sixes it's the coil… Moderate P0357 Powertrain Coil G, which fires cylinder 7 on V8s, has an electrical fault. On GM trucks it sits by… Moderate P0365 Powertrain The exhaust cam sensor on bank 1 has lost its signal. Usually a heat-damaged sensor… Low P0366 Powertrain Bank 1 exhaust cam signal is out of position: chain stretch, a sticky exhaust phaser… Moderate P0402 Powertrain More exhaust is being recirculated than the ECU asked for, usually because the EGR valve won't… Moderate