Car won't start (cranks but no fire)
Starter cranks fine, but the engine won't catch. What OBD-II shows and which codes to check.
If the starter cranks normally but the engine doesn't catch, in 99% of cases one of three things is missing: spark, fuel, or the basic crank/cam reference signal.
OBD-II is limited in this scenario — with the engine not running, many PIDs don't update. But stored DTCs are available: plug in the adapter and read Mode 03. Common codes: P0335 (CKP sensor), P0340 (CMP), or U-series communication codes.
Practical test: crank for 5-10 seconds, let the code set. Now open freeze frame — you'll see RPM 0 and all parameters at the moment of the failed start.
First diagnostic steps
- Try to start and read stored + pending DTCs
- Check battery voltage while cranking (spec > 9.5V)
- Listen for the fuel pump priming for 2-3 sec after ignition ON
- Pull a spark plug and check for spark against ground while cranking
- If any pending U-code — start with the OBD-II connector and battery ground
Likely fault codes
Click a code for detailed description, causes, and diagnostic plan.