Car won't start: Codes, Causes & Fixes

First tell the two cases apart: if the engine does not crank at all, the battery, battery terminals, starter or a security/immobilizer lockout are the usual suspects; if it cranks but won't fire, look at fuel delivery, crankshaft position sensor and ignition. Codes such as P0335 (crankshaft sensor) or immobilizer messages narrow it down, but a no-crank fault may leave no code at all. Check battery voltage and terminal connections before anything else.

123Codes

3.2Average severity

28%High or critical

21%DIY-friendly

Severity distribution

Most viewed

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 P0606 Powertrain The engine computer failed its own internal self-test – check its power and grounds before… 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

All codes (106)

All Severity 3+ Severity 4+

P3191 Toyota · Powertrain The hybrid system spun the gas engine with its motor-generator, but the engine never fired up. High U0001 Network A module found the high-speed CAN network itself misbehaving, not just one silent module. High 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 U0103 Network The electronic shifter (dial, knob or joystick) stopped talking to the transmission and engine… High U0105 Network The PCM lost contact with the separate module that fires the injectors, common on diesel… High U0109 Network The PCM lost contact with the module that controls fuel pump speed; stalling or no-start can… High U0110 Network The hybrid/EV system lost contact with the module that runs electric drive motor A. Critical U0115 Network Modules lost contact with the second engine computer on vehicles that use two of them. High U0140 Network Other modules stopped hearing from the body control module that runs lights, locks, wipers… Moderate U0141 Network A body module labeled "A" went silent; on many trucks and SUVs it is the smart fuse box under… Moderate U0146 Network The central gateway that links the car's networks went silent, so many modules report errors… Moderate U0404 Network The electronic shifter reports a lever position the transmission can't trust, so Park may not… High U1000 Chevrolet · Network A module on an older GM's Class 2 data line couldn't communicate, so modules stopped hearing… Moderate U1000 Nissan · Network A Nissan control module couldn't send or receive CAN messages for about 2 seconds or longer. Moderate U1064 Chevrolet · Network Other modules stopped hearing the body control module on an older GM's Class 2 data line. Moderate

Symptoms

Check engine light on 558 Loss of power 214 Rough idle 184 Limp mode 165 Poor fuel economy 146 Engine stalling 133 Harsh or slipping shifts 80 ABS / traction light on 65 Fuel smell 34 Check engine light flashing 22