Rough idle: Codes, Causes & Fixes

P0174 Powertrain The cylinder bank without cylinder 1 is running lean even with the maximum fuel correction… Moderate 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 P0172 Powertrain The engine computer is pulling as much fuel as it's allowed on bank 1 and the mixture is still… 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

P0301 Powertrain Cylinder 1 is repeatedly failing to fire. The cause is almost always its coil, plug, injector… Moderate 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 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 P0321 Powertrain The rpm signal is there but erratic: extra or missing pulses the computer can't trust. Expect… Moderate P0335 Powertrain The engine computer lost the crankshaft position signal. Expect stalling or a crank-no-start. High P0336 Powertrain Crank signal present but implausible: damaged teeth, a slipped balancer ring or debris confuse… Moderate P0338 Powertrain The crank signal line sits at 5 or 12 volts and stops switching: open ground, open wire… High P0341 Powertrain The bank 1 cam signal lands at the wrong crank angle, often from a stretched chain or a sticky… Moderate P0344 Powertrain The bank 1 cam sensor signal keeps dropping out for short moments, which can cause random… 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 P0350 Powertrain The shared coil feed, ignition module or coil wiring is faulty. Often set with several… 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 P0354 Powertrain Coil D, normally the one on cylinder 4, failed its circuit check. It often shows up right after… 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 P0358 Powertrain Coil H, for cylinder 8, has an electrical fault. On nearly every V8 it's the hardest coil… Moderate P0366 Powertrain Bank 1 exhaust cam signal is out of position: chain stretch, a sticky exhaust phaser… Moderate P0369 Powertrain The bank 1 exhaust cam signal drops out now and then. Usually heat or vibration at the sensor… Low P0380 Powertrain The diesel glow plug circuit A (relay, fuse, wiring or the plugs as a group) isn't drawing… Low