Cylinder 1 Glow Plug Control Circuit High
The P066B code indicates that the powertrain control module (PCM) has detected a high voltage condition in the glow plug control circuit for cylinder 1. This circuit controls the glow plug, which heats the combustion chamber to aid cold starts in diesel engines. A high voltage reading suggests a short to power, faulty glow plug, or a problem with the glow plug control module.
1. Most Common Causes
- Short to power in the glow plug circuit
- Faulty glow plug (cylinder 1)
- Failed glow plug control module
- Corroded or damaged wiring/connectors
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting, especially in cold weather
- Rough idle or misfire on cylinder 1
- Reduced fuel economy
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm P066B 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; compare to specs (typically 0.5-2 ohms).
Step 4: Check voltage at the glow plug connector with key on; should be battery voltage. If high, suspect short to power.
Step 5: Test the glow plug control module output for cylinder 1.
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 glow plug system or PCM.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether it's a simple wiring repair or glow plug replacement.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.