Symptoms of P0347
- 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 P0347
- 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 sensor supply voltage, ground, signal voltage, connector condition, cam signal on a scope, and freeze-frame conditions when the low input occurred.
- Inspect for short-to-ground faults, open supply circuits, oil intrusion, damaged wiring, poor terminal fit, and sensor target damage.
- Compare the signal at the sensor and PCM connector to isolate whether the low input is caused by the sensor, harness, or controller input.
Related OBD-II codes
These nearby ignition / misfire entries can help compare wording and pin down the fault area.