Cylinder 2 Glow Plug Control Circuit High
The P066D code indicates that the powertrain control module (PCM) has detected a high voltage condition in the glow plug control circuit for cylinder 2. This circuit controls the glow plug, which preheats the combustion chamber in diesel engines for cold starts. A high voltage reading suggests a short to power, faulty glow plug, or a problem with the glow plug control module. This can lead to hard starting, misfires, and increased emissions.
01. Most Common Causes
- Faulty glow plug in cylinder 2
- Short to power in the glow plug control circuit
- Failed glow plug control module
- Corroded or damaged wiring/connectors
02. Symptoms You Will Notice
- Hard starting, especially in cold weather
- Engine misfire or rough idle
- Check Engine Light illuminated
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve the code and check for additional codes.
Step 2: Visually inspect the glow plug wiring and connector for cylinder 2 for damage or corrosion.
Step 3: Test the glow plug resistance with a multimeter; compare to specifications.
Step 4: Check the glow plug control module for proper operation and voltage output.
04. Commonly Affected Makes
05. 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, misfires, and potential damage to the glow plug system. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether a glow plug or wiring repair is needed.