Check engine light on: 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 P0113 Powertrain The intake air temperature signal is stuck at maximum voltage, which usually means an open… Low P0135 Powertrain The heater inside the upstream oxygen sensor on bank 1 isn't working or its circuit is faulty. Low P0171 Powertrain The engine computer is adding the maximum extra fuel it's allowed on bank 1 and still sees… Moderate

P052E Powertrain The crankcase ventilation regulator isn't controlling crankcase pressure properly – often… Moderate P0532 Powertrain The A/C pressure sensor reads too low – often a low refrigerant charge, sometimes a wiring… Low P0533 Powertrain The A/C high-side pressure reads too high – often a dead cooling fan, clogged condenser… Low P0550 Powertrain The engine computer lost a believable power steering pressure switch signal; idle may dip when… Low P0560 Powertrain The engine computer saw its supply voltage missing or out of range – check fuses and feeds… Moderate P0561 Powertrain System voltage jumps up and down instead of holding steady – often loose terminals… Low P0562 Powertrain The engine computer sees too little supply voltage – usually a charging, battery or ground… Moderate P0563 Powertrain The engine computer sees too much supply voltage – usually an overcharging alternator cooking… Moderate P0571 Powertrain The engine computer doesn't trust the brake pedal switch signal – cruise control usually stops… Low P0572 Powertrain The PCM never sees the brake pedal pressed – brake lights may be out and the car may not shift… Moderate P0573 Powertrain The PCM thinks the brake pedal is always pressed – brake lights stay on, often from a missing… Moderate P0597 Powertrain The electrically heated thermostat's heater circuit is open, so the ECU can't open it early… Low P0600 Powertrain The engine computer lost a dedicated data link to another module, most often the transmission… Moderate P0601 Powertrain The engine computer's stored software failed its checksum test at start-up – usually a reflash… Moderate P0602 Powertrain The engine computer has no valid or complete software – typical after a module swap or a failed… Moderate P0603 Powertrain The engine computer lost its learned memory – usually after a battery disconnect or a bad… Low P0604 Powertrain The engine computer's working memory failed a read/write test – rarely a software issue, often… Moderate P0605 Powertrain The memory holding the engine computer's program failed its integrity test – try one reflash… Moderate P0606 Powertrain The engine computer failed its own internal self-test – check its power and grounds before… Moderate P0607 Powertrain A general internal performance check in the engine computer failed – supply, grounds… Moderate P0610 Powertrain The engine computer's vehicle configuration is missing or doesn't match the car – usually after… Low P061B Powertrain The ECM's safety monitor disagreed with its own engine torque calculation – often bad input… Moderate P0620 Powertrain The engine computer found a fault in the wire or signal it uses to command alternator output. Moderate P0621 Powertrain A fault in the alternator's 'L' circuit – the line behind the charge light or the ECM's turn-on… Moderate P0622 Powertrain The alternator's field control or field feedback circuit is faulty – output may drop out… Moderate P0625 Powertrain The PCM sees the alternator's field-monitor signal stuck low – usually the regulator, its plug… Moderate P0626 Powertrain The alternator reports a field signal stuck at or near full output – battery, alternator… Moderate P0627 Powertrain The PCM's fuel pump command line has no complete circuit – a dead relay coil, open wire, fuse… Moderate P0628 Powertrain The fuel pump control wire is pulled toward ground – a chafed wire, shorted relay coil or wet… Moderate P0629 Powertrain Battery voltage is leaking into the fuel pump control line – a short, corrosion bridge… Moderate