Cylinder 4 Glow Plug Control Circuit High
The P067B code indicates that the engine control module (ECM) has detected a high voltage condition in the glow plug control circuit for cylinder 4. This typically means the circuit has a short to voltage or a faulty glow plug module. Glow plugs are used in diesel engines to preheat the combustion chamber for cold starts. A high circuit condition can prevent the glow plug from functioning properly, leading to hard starting, misfires, and increased emissions.
1. Most Common Causes
- Faulty or internally shorted glow plug in cylinder 4
- Short to voltage in the control circuit wiring
- Loose, corroded, or poor ground electrical connection
- Defective glow plug relay or control module
- Faulty PCM or controller (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting, especially in cold weather
- Rough idle or misfire on cylinder 4
- Reduced fuel economy and increased emissions
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve the code and check for other related codes.
Step 2: Visually inspect the glow plug wiring and connector for cylinder 4 for damage, corrosion, or shorts.
Step 3: Measure the resistance of the glow plug for cylinder 4; compare to specifications (typically 0.5-2 ohms).
Step 4: Check for voltage at the glow plug connector with the ignition on; should be battery voltage for a few seconds.
Step 5: Test the glow plug control module/relay for proper operation and output voltage.
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. In cold weather, the vehicle may not start at all.
How much does it cost to fix?▼
The cost to fix P067B typically ranges from $50 to $150 for parts and labor, depending on whether it's a simple wiring repair or replacement of a glow plug or control module.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.