What it means
An electrical fault has been detected in the ignition coil circuit for cylinder 4 — open primary winding, short to ground, or short to supply. The ECU disables the coil to protect its driver and the cylinder misfires.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The ignition module switches current through the primary winding of coil D, which serves cylinder 4, so the coil can produce a spark for that cylinder. The control module monitors this circuit and sets P0354 when it detects an open or a short to ground or supply in the cylinder 4 coil circuit.
Common causes
Most likely first.
- Coil primary winding open or shorted
- Wiring or connector fault
Symptoms
- Check-engine light
- Rough running or misfire
- Hard starting
- Reduced engine power
How to diagnose it
- Capture freeze-frame data and check cylinder 4 misfire counts with a scan tool before clearing the code.
- Inspect coil D, its connector, and the wiring to it for loose or backed-out pins, corrosion, chafing, or heat damage.
- Check the coil D supply and control circuits for an open or short, following the wiring diagram and manufacturer's specification.
- Measure coil D's primary winding and compare the result with the manufacturer's specification.
- If the coil and harness pass, test the control module's coil D driver and connections using the manufacturer's diagnostic procedure.
Common fixes
- Reconnect the cylinder 4 coil connector and secure it.
- Repair damaged wiring or connector terminals in the coil D circuit.
- Replace coil D if its primary winding fails the specified test.
- Repair the coil D driver circuit or replace the control module if a driver fault is confirmed.
Can I keep driving?
Do not continue driving if cylinder 4 is misfiring badly or the check-engine light flashes; continued misfire can overheat the catalytic converter. With a steady light and smooth running, limit use and arrange prompt diagnosis.
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.