Ignition Coil G Primary/Secondary Circuit Malfunction
The P0357 code indicates a malfunction in the primary or secondary circuit of ignition coil G. This coil is responsible for providing the spark to cylinder 7 (or the corresponding cylinder in your engine's firing order). The Powertrain Control Module (PCM) monitors the voltage and current in the coil's primary circuit. When it detects an abnormal condition—such as an open or short circuit, excessive resistance, or a faulty coil driver—it sets this code. This can lead to misfires, reduced engine performance, and increased emissions.
1. Most Common Causes
- Faulty ignition coil G (damaged primary or secondary winding)
- Corroded, damaged, or disconnected wiring or connector for coil G
- Short to ground or voltage in the coil control circuit
- Open circuit in the primary or secondary winding wiring
- Rare but possible ECM/PCM failure
- Defective spark plug with abnormal resistance affecting the secondary circuit
2. Symptoms You Will Notice
- Engine misfire (especially under load)
- Check Engine Light illuminated
- Rough idle or hesitation during acceleration
- Decreased fuel economy
3. Step-by-Step Diagnosis
Step 1: Scan for codes and note any additional misfire codes (e.g., P0307 for cylinder 7 misfire).
Step 2: Visually inspect the ignition coil G wiring and connector for damage, corrosion, or loose connections.
Step 3: Swap coil G with another coil (e.g., coil A) and clear codes. If the code moves to the new cylinder (e.g., P0351), replace the coil.
Step 4: If the code remains on cylinder G, test the power and ground circuits at the coil connector using a multimeter (should see battery voltage with key on, and good ground).
Step 5: If circuits are okay, test the PCM's coil driver by checking for a pulsed ground signal (using a test light or oscilloscope) while cranking. If no signal, suspect PCM failure.
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 cause poor performance. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
Typically $50-$150 for a DIY coil replacement. Shop labor adds $100-$200, so total could be $150-$350.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.