Car won't start: Codes, Causes & Fixes

P0335 Powertrain The engine computer lost the crankshaft position signal. Expect stalling or a crank-no-start. High P0340 Powertrain The computer lost the camshaft signal on bank 1. Expect long cranking, less power… Moderate P0562 Powertrain The engine computer sees too little supply voltage – usually a charging, battery or ground… Moderate U0073 Network A module saw so many errors on CAN bus A that it shut off its own transmitter. High U0100 Network Another module stopped hearing from the engine computer on the CAN network. High P0606 Powertrain The engine computer failed its own internal self-test – check its power and grounds before… Moderate

P0380 Powertrain The diesel glow plug circuit A (relay, fuse, wiring or the plugs as a group) isn't drawing… Low P0381 Powertrain The circuit for the dash wait-to-start light has a fault. The glow plugs themselves may still… Minor P0496 Powertrain Vapor is being drawn into the engine while purge is commanded off: almost always a purge valve… Low P0504 Powertrain The two contacts in the brake pedal switch disagree on whether you're braking; check the pedal… Moderate P0511 Powertrain The computer can't drive the idle air control valve properly – typically an open winding… Low P0560 Powertrain The engine computer saw its supply voltage missing or out of range – check fuses and feeds… Moderate P0562 Powertrain The engine computer sees too little supply voltage – usually a charging, battery or ground… Moderate 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 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 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 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 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 P0630 Powertrain The engine computer has no VIN stored, or one that doesn't match the car – a classic after… Low P0641 Powertrain The PCM's shared 5-volt supply 'A' is missing or out of range – often one shorted sensor… High P0642 Powertrain The PCM's 5-volt supply 'A' is being pulled below spec, usually by a short to ground in one… High P0670 Powertrain The engine computer can't properly control or hear back from the diesel's glow plug control… Low P0671 Powertrain The glow plug in cylinder 1 or its wire isn't drawing normal current. Usually the plug itself… Low P0685 Powertrain The engine computer can't switch its own main power relay – open coil, blown fuse or broken… High P0686 Powertrain The main relay control line is being pulled to ground – usually a shorted relay coil… Moderate P0687 Powertrain The main relay control line sits at battery voltage – the relay may never switch on or never… Moderate P0690 Powertrain The ECM still sees power coming through its main relay when the relay should be off – often… Low