Cylinder 3 Glow Plug Control Circuit High
The P066F code indicates that the powertrain control module (PCM) has detected a high voltage condition in the glow plug control circuit for cylinder 3. This typically means the circuit has excessive resistance or a short to voltage, preventing proper glow plug operation. Common causes include a faulty glow plug, damaged wiring or connector, or a failed glow plug control module. This issue is most prevalent in diesel engines, especially during cold starts.
01. Most Common Causes
- Faulty glow plug in cylinder 3
- Damaged wiring or connector in the glow plug circuit
- Failed glow plug control module
- Corrosion or loose connection at the glow plug
02. Symptoms You Will Notice
- Hard starting, especially in cold weather
- Check Engine Light illuminated
- Rough idle or misfire on cylinder 3
- Excessive white smoke from exhaust on startup
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the glow plug wiring and connector for cylinder 3 for damage or corrosion.
Step 3: Test the glow plug resistance using a multimeter (should be low, typically 0.5-2 ohms).
Step 4: Check for voltage at the glow plug connector with the key on (should see battery voltage for a few seconds).
Step 5: If voltage is present and glow plug is good, test the glow plug control module output for cylinder 3.
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, increased emissions, and potential damage to the glow plug system. Have it diagnosed and repaired promptly.
How much does it cost to fix?▼
The cost to fix P066F typically ranges from $50 to $150, depending on whether it's a simple glow plug replacement or more complex wiring repair. Labor and parts costs vary by vehicle.