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
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
All codes (123)
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
U3003
Network
A control module saw its supply voltage drop too low or rise too high, usually a battery…
Low