Engine stalls while driving
Engine cuts out unexpectedly while moving — a dangerous symptom. First steps and OBD-II codes.
A sudden engine stall while driving is a safety event — brake booster and power steering both go offline. Get the car safely stopped, then diagnose.
Causes: (1) crankshaft position sensor (CKP) failure — engine loses sync; (2) MAP sensor failing under certain loads; (3) fuel pump failing hot (thermal failure); (4) ignition coil failure under load; (5) ECU power supply issue (ground strap or main relay).
OBD-II key moment: frozen DTCs immediately after stall. Connect before restarting — pending and stored codes at that moment are the most informative.
First diagnostic steps
- Connect OBD-II adapter BEFORE restarting — read all codes
- Check STFT/LTFT just before stall if you have a live-log session
- Check battery voltage and engine ground strap connection
- Test fuel pressure: does the rail hold pressure after pump shuts off (should hold 30+ sec)
- Inspect CKP sensor connector and reluctor ring gap
Likely fault codes
Click a code for detailed description, causes, and diagnostic plan.