Ignition Coil D Primary/Secondary Circuit Malfunction
The P0354 code indicates a malfunction in the primary or secondary circuit of ignition coil D (typically coil for cylinder 4). This circuit includes the coil itself, its power supply, ground, and the control signal from the engine control module (ECM). A fault can cause weak or no spark, leading to misfires, reduced engine performance, and increased emissions.
1. Most Common Causes
- Faulty ignition coil D (internal open or short in primary or secondary winding)
- Damaged, corroded, or high-resistance wiring or connector in coil D circuit
- Short to ground or voltage in the coil control circuit
- Defective ignition system power relay
- Poor ground connection in the coil circuit
- Intermittent ECM/PCM failure (less common)
- Faulty spark plug causing excessive load on the secondary circuit
2. Symptoms You Will Notice
- Engine misfire (cylinder 4)
- Check Engine Light on
- Rough idle, hesitation, or loss of power
- Increased fuel consumption
3. Step-by-Step Diagnosis
Step 1: Scan for codes and verify P0354 is present.
Step 2: Inspect ignition coil D and its wiring for damage, corrosion, or loose connections.
Step 3: Swap coil D with another cylinder and see if the code moves; if so, replace the coil.
Step 4: Check power and ground at coil connector with a multimeter (12V with key on, good ground).
Step 5: Test the ECM control signal using a lab scope or test light; if missing, check wiring and ECM.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with a misfire can damage the catalytic converter and reduce fuel economy. Have it diagnosed promptly.
How much does it cost to fix?▼
Typically $50-$150 for a DIY coil replacement. Shop labor may add $50-$100, totaling $100-$250.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.