Cylinder 1 Glow Plug Control Circuit Low
The P066A code indicates that the powertrain control module (PCM) has detected a low voltage condition in the glow plug control circuit for cylinder 1. This circuit is responsible for energizing the glow plug to aid cold starts in diesel engines. A low voltage reading suggests a short to ground, open circuit, or faulty component, which can prevent the glow plug from heating properly, leading to hard starting, misfires, and increased emissions.
1. Most Common Causes
- Faulty glow plug in cylinder 1
- Open or shorted wiring in the glow plug control circuit
- Failed glow plug relay or control module
- Corroded or loose electrical connector at the glow plug
2. Symptoms You Will Notice
- Hard starting, especially in cold weather
- Engine misfire or rough idle
- Check Engine Light illuminated
- Excessive smoke from exhaust during startup
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm the code and check for related codes.
Step 2: Visually inspect the glow plug wiring and connector for cylinder 1 for damage or corrosion.
Step 3: Measure resistance of the glow plug; should be low (typically 0.5-2 ohms). Replace if open or shorted.
Step 4: Test voltage at the glow plug connector with key on; should be battery voltage. If low, check relay and wiring.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code, as it can cause hard starting, poor engine performance, and potential damage to the catalytic converter from unburned fuel.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for a DIY glow plug replacement, or $100 to $300 if professional labor is required.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.