What it means
Ignition F control signal stuck high — short to B+. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Ignition F is a designated ignition-coil control channel; the letter does not identify a universal cylinder. The control module monitors the F control-signal circuit and sets this code when its signal is higher than expected, which can happen if the wire is shorted to battery voltage.
Common causes
Most likely first.
- Short to B+
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine light on or flashing
- Engine misfire or rough running
- Power loss or hesitation
- Hard starting
How to diagnose it
- Record freeze-frame data and check live misfire counts to determine whether the F-channel fault is affecting engine operation.
- Inspect the Ignition F coil connector and harness for pinched wiring, chafing against a power feed, water, corrosion, or backed-out pins.
- While monitoring the F control signal, gently move the harness to see whether the reading changes with movement.
- With the circuit isolated as specified by the manufacturer, check whether the F control wire is shorted to battery voltage.
- If wiring and connector checks pass, test the F coil and module driver using the manufacturer's procedure.
Common fixes
- Repair pinched or chafed F-channel wiring that is touching a power source.
- Clean and dry the connector and repair corroded, loose, or pushed-back terminals.
- Replace the F coil if it fails the manufacturer's tests.
- Repair or replace the module only after confirming its F-channel driver is faulty.
Can I keep driving?
If the engine misfires, avoid hard acceleration and stop driving if the check-engine light flashes, since continued misfire can damage the catalytic converter. With a steady light and smooth running, limit driving and have the 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.