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 a failed glow plug control module. This issue primarily affects diesel engines, leading to hard starting, especially in cold weather.
1. Most Common Causes
- Faulty glow plug in cylinder 3
- Short to voltage in the glow plug circuit
- Damaged wiring or connector at cylinder 3
- Failed glow plug control module
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting, especially in cold weather
- Rough idle or misfire on cylinder 3
- Excessive smoke from exhaust during startup
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data. Clear code and test drive to see if it returns.
Step 2: Visually inspect the glow plug wiring and connector at cylinder 3 for damage, corrosion, or loose connections.
Step 3: Measure resistance of cylinder 3 glow plug; compare to manufacturer specs (typically 0.5-2 ohms). Replace if out of range.
Step 4: Check for voltage at the glow plug connector with key on; if voltage is present but glow plug is good, suspect a short elsewhere. If no voltage, test the glow plug control module and related fuses.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances, especially in cold weather, as the engine may be hard to start and could run poorly. Continued driving may cause further damage to the glow plug system or catalytic converter.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for a DIY glow plug replacement. If professional diagnosis and repair are needed, including control module replacement, costs can be $200-$500.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.