Ignition Coil A Primary/Secondary Circuit Malfunction
The P0351 code indicates a malfunction in the primary or secondary circuit of ignition coil 'A' (typically coil #1). The Powertrain Control Module (PCM) monitors the voltage and current in the coil's primary circuit. If the PCM detects an open, short, or excessive resistance in the coil or its wiring, it sets this code. This can cause misfires, rough running, and reduced fuel economy.
1. Most Common Causes
- Faulty ignition coil
- Open or shorted wiring in the coil circuit
- Poor electrical connection at the coil connector
- Failed PCM (rare)
2. Symptoms You Will Notice
- Engine misfire
- Rough idle
- Check Engine Light on
- Reduced engine power and fuel economy
3. Step-by-Step Diagnosis
Step 1: Scan for codes and note freeze frame data.
Step 2: Visually inspect ignition coil and wiring for damage or corrosion.
Step 3: Test coil primary and secondary resistance with a multimeter.
Step 4: Swap coil with another cylinder to see if misfire moves.
Step 5: Check power and ground at coil connector with a test light.
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?▼
Replacing an ignition coil typically costs $50-$150 for parts and labor, depending on vehicle make and model.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.