What does it mean?
P1315 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Ignition Coil 4 Primary Feedback Circuit Malfunction .
Symptoms
- MIL (check engine lamp) on, flashing when the misfire becomes severe
- Misfire on cylinder 4 with a rough, shaking idle
- Hesitation, loss of power and poor throttle response
- Hard starting, occasional stalling or cut-out
- Fuel smell from the tailpipe and increased consumption, with a risk of catalyst damage if ignored
Likely causes
- Coil 4 primary winding or integrated igniter failed
- Feedback or trigger wire between coil 4 and the module open, shorted or with high resistance
- Corroded or loose coil connector, or oil sitting in the plug well
- Missing battery supply to the coil from a blown fuse, failed relay or a damaged feed wire
- Poor ignition system ground
- Failed ignition control module output for coil 4
- Engine control module driver fault, only after the circuit is proven good
How to fix it
- Read the freeze frame and confirm the affected cylinder with live misfire counters
- Swap coil 4 with a coil from another cylinder and see whether the code moves
- Check supply voltage and ground at the coil connector with the key on
- Test the trigger and feedback wires for continuity and for shorts to ground or battery
- Inspect the plug well and boot for oil, moisture and carbon tracking, and read the spark plug
- Replace the coil or repair the harness fault, then re-evaluate the ignition module if the code persists
- Clear the codes and confirm on a road test that no misfire counts accumulate