What does it mean?
Coil L is the twelfth designation in the ignition coil list, so this code belongs to engines with a large number of coil outputs, and which physical cylinder it serves depends on the manufacturer's numbering. The control module drives the coil's primary winding and monitors the current that builds in it and the voltage that appears when the magnetic field collapses; on many systems it also evaluates feedback from the secondary side. P0364 is stored when that electrical behaviour is wrong: the primary current does not build or does not collapse as expected, or the secondary demand falls outside the calibrated window. The fault can therefore lie in the coil itself, in the wiring that feeds and triggers it, or in the secondary path between the coil and the spark plug.
Symptoms
- Misfire on the affected cylinder, felt as shaking at idle and jerking under load
- MIL on and flashing during heavy misfire, which warns of catalytic converter damage
- Loss of power, poor acceleration and hesitation when pulling away
- Hard starting, especially when the engine is cold or the weather is damp
- Increased fuel consumption and a smell of unburnt fuel from the exhaust
- Occasional popping from the exhaust on deceleration
Likely causes
- Failed ignition coil with an open, shorted or heat damaged winding
- Worn spark plug with an excessive gap forcing an abnormally high secondary voltage
- Damaged, cracked or carbon tracked coil boot, or a boot flooded with oil
- Open or high resistance in the coil supply, ground or trigger wire
- Corroded, wet or loose coil connector, common on the rearmost and hardest to reach coils
- Chafed ignition harness shorting to ground or to another circuit
- Control module ignition driver fault, considered only after everything external has been tested
How to fix it
- Read the misfire counters together with this code to confirm which cylinder is affected
- Remove the coil and inspect the boot, spring and spark plug for carbon tracking, cracks, oil and an incorrect gap
- Measure the coil primary and secondary resistance where the manufacturer publishes values, and compare with a good coil from the same engine
- Check supply voltage and ground at the coil connector and test the trigger wire for continuity and voltage drop
- Swap the coil with a neighbouring cylinder and re-test; if the misfire moves, the coil is at fault
- Inspect the spark plug well for oil and renew the tube seal before fitting a new coil
- Renew the failed coil and plug, then clear the code and confirm over a road test that includes load