What does it mean?
P1301 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cylinder 1 Misfire Detected . This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms
- MIL (check engine lamp) on, and flashing while the misfire is active; a flashing lamp means stop driving to protect the catalytic converter
- Rough idle with vibration felt through the body and steering wheel
- Stumble, hesitation and power loss on acceleration
- Higher fuel consumption and a fuel smell from the tailpipe
- Uneven exhaust note with occasional popping
Likely causes
- Worn, fouled or incorrectly gapped spark plug on cylinder 1
- Failing ignition coil, or a cracked and carbon-tracked coil boot on that cylinder
- Clogged, leaking or electrically dead fuel injector on cylinder 1
- Vacuum leak at that intake runner, the injector seal or a nearby gasket
- Low compression from a burnt valve, worn rings, tight valve clearance or a failing head gasket
- Low fuel pressure or contaminated fuel affecting the whole engine but showing worst on one cylinder
- Damaged wiring or a loose connector at that cylinder's coil or injector
How to fix it
- Confirm with live misfire counters that cylinder 1 is the one counting, and note the freeze frame conditions
- Swap the coil with a neighbouring cylinder, clear the codes and see whether the misfire moves
- Do the same with the injector if the coil swap changes nothing
- Remove and read the spark plug: check the gap and look for oil, coolant or fuel fouling
- Smoke test the intake for a vacuum leak around that runner and the injector seal
- Verify fuel pressure and test the injector for resistance and spray quality
- Run a compression test and, if it is low, a leak-down test on cylinder 1 to find where the pressure is escaping