Ignition Coil D Primary/Secondary Circuit
The Powertrain Control Module (PCM) has detected a malfunction in the primary or secondary electrical circuit of ignition coil 'D', which typically corresponds to cylinder number 4. This code is set when the PCM does not receive the expected voltage pulse signal from the ignition coil circuit, indicating a failure to properly fire the spark plug.
Driving with an active ignition coil circuit code can lead to severe engine misfires. Unburned fuel entering the exhaust system can quickly overheat and permanently damage the catalytic converter.
Common symptoms
- Illuminated or flashing Check Engine Light
- Engine misfire resulting in a rough idle
- Noticeable lack of engine power during acceleration
- Engine hesitation or stumbling under load
- Decreased fuel economy and strong exhaust odor
Likely causes
- Defective ignition coil 'D' (typically cylinder 4)
- Damaged, corroded, or loose wiring connector at the ignition coil
- Broken, chafed, or shorted wiring in the ignition coil 'D' circuit
- Faulty or excessively worn spark plug in the affected cylinder
- Failing Powertrain Control Module (PCM) or internal coil driver (rare)
What to check before replacing parts
Inspect the wiring and connector at ignition coil 'D'.
Look for: Look for loose pins, broken wires, melted plastic, or corrosion that could interrupt the electrical connection to the coil.
Swap ignition coil 'D' with another cylinder's coil (e.g., coil 'A'), clear the codes, and test drive.
Look for: If the trouble code moves to the new cylinder (e.g., setting a P0351), the ignition coil itself is faulty and requires replacement.
Test the ignition coil connector for proper power and ground using a digital multimeter.
Look for: With the ignition on, verify that the coil is receiving battery voltage and a solid ground. A lack of voltage indicates an upstream wiring, fuse, or relay issue.
Check the trigger signal from the PCM to the ignition coil using a noid light or oscilloscope.
Look for: A consistent pulsing signal while cranking or running indicates the PCM and trigger wiring are good. No pulse suggests a broken trigger wire or a faulty PCM driver.
Remove and inspect the spark plug for the affected cylinder.
Look for: Check for a cracked ceramic insulator, fouled electrode, or excessive gap that could cause high secondary circuit resistance and stress the coil.
This page explains the generic P0354 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
Gear guide: Best OBD2 ScannersRead this code yourself next time — from $20 Bluetooth dongles to bidirectional scan tools.Rather have a pro handle it? Find a vetted local mechanic.