Symptoms of P0338
- Rough idle, shaking, or a stumble under acceleration.
- A flashing check-engine light during an active misfire.
- Power loss and higher fuel consumption.
Common causes of P0338
- Worn spark plugs, ignition coils, or plug wires.
- Fuel-delivery problems — injectors, pressure, or a lean/rich mixture.
- Vacuum leaks, low compression, or a mechanical fault in that cylinder.
Useful checks before replacing parts
- Check for short-to-voltage, open ground, connector damage, and harness chafing near the crank sensor.
- Compare RPM and crank signal data during key-on, cranking, and running conditions.
- Inspect sensor mounting, trigger wheel condition, and recent service work that may have disturbed wiring.
Related OBD-II codes
These nearby ignition / misfire entries can help compare wording and pin down the fault area.