What it means
An electrical fault is detected in both the primary and the secondary circuit of ignition coil F. The ECU cannot drive the coil correctly, so the cylinder served by coil F misfires or does not fire at all. Causes: an open or shorted primary control wire, an internal coil winding fault, a failed igniter/driver, or wiring or connector damage at the coil.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Coil F's primary circuit carries switched current to build the magnetic field that produces spark for its assigned cylinder. The control module monitors the coil F primary and secondary circuit response and sets P0356 when it detects an electrical fault that can stop that cylinder from firing.
Common causes
Most likely first.
- Ignition coil F failure
- Open, shorted, or damaged coil wiring
- Loose or corroded connector
- Fault in the ignition control driver
Symptoms
- Check engine light on or flashing
- Engine misfire or rough running
- Power loss or hesitation
- Hard starting
How to diagnose it
- Save freeze-frame data and review misfire counts with a scan tool to determine whether a particular cylinder is affected.
- Inspect coil F, its connector, and nearby harness for loose pins, corrosion, chafing, or heat damage.
- Check coil F's supply and control circuits for opens or shorts using the wiring diagram and manufacturer's specification.
- Test the coil F primary and secondary paths according to the manufacturer's procedure.
- If the coil and wiring are within specification, check the ignition control driver and its module connections.
Common fixes
- Secure or reconnect the coil F connector.
- Repair damaged wiring or corroded terminals in the coil F circuit.
- Replace coil F if its winding or secondary path fails testing.
- Repair the control driver wiring or replace the module if a driver fault is confirmed.
Can I keep driving?
Do not keep driving with a severe misfire or a flashing check-engine light; unburned fuel can overheat the catalytic converter. If the engine is smooth and the light stays on steadily, minimize trips and have the coil F circuit checked soon.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.