Rough idle: Codes, Causes & Fixes

P0174 Powertrain The cylinder bank without cylinder 1 is running lean even with the maximum fuel correction… Moderate P0300 Powertrain The engine computer sees misfires that jump between cylinders or hit several cylinders at once. High 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 P0302 Powertrain Cylinder 2 keeps misfiring. On inline engines it's a middle cylinder, so rule out coolant… Moderate

P0204 Powertrain The circuit to injector 4 is open or out of range; on most transverse engines that's… Moderate P0205 Powertrain The ECU sees a broken or faulty electrical circuit to the cylinder 5 injector, so that cylinder… Moderate P0206 Powertrain Injector 6's circuit is open or faulty. On an inline-six that's the rear cylinder, tucked under… Moderate P0207 Powertrain The ECU lost normal control of injector 7, which only exists on V8 and larger engines. Moderate P0208 Powertrain The circuit to injector 8, the rear cylinder on bank 2 of a V8, is open or doesn't respond… Moderate P0219 Powertrain The engine was spun faster than its maximum allowed rpm, usually by a missed shift or wheelspin. Moderate P0221 Powertrain The second throttle angle signal leaves its window or stops following the plate, so power… Moderate P0263 Powertrain Cylinder 1 is producing noticeably more or less power than the others, beyond what fuel trim… Moderate P0266 Powertrain The engine computer can't even out cylinder 2 with fuel corrections; its balance rate is past… Moderate P0269 Powertrain Cylinder 3 isn't pulling its weight, or is pulling too hard, and the fuel correction for it… Moderate P0272 Powertrain The ECU can't balance cylinder 4 against the rest anymore; its fuel correction is outside… Moderate P0275 Powertrain The fuel correction for cylinder 5 is past its limit. Only engines with five or more cylinders… Moderate P0300 Powertrain The engine computer sees misfires that jump between cylinders or hit several cylinders at once. High 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 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