Cylinder 8 Glow Plug Control Circuit Low
The P068E code indicates that the powertrain control module (PCM) has detected a low voltage condition in the glow plug control circuit for cylinder 8. This circuit is responsible for supplying power to the glow plug, which aids in cold starting by heating the combustion chamber. A low voltage reading suggests excessive resistance, a short to ground, or a faulty component, preventing the glow plug from reaching the required temperature. This can lead to hard starting, misfires, and increased emissions, especially in cold weather.
1. Most Common Causes
- Faulty glow plug in cylinder 8
- Open or shorted glow plug wiring harness
- Corroded or loose electrical connector at glow plug
- Failed glow plug control module or relay
- PCM software or hardware issue
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting, especially in cold weather
- Engine misfire or rough idle
- Reduced fuel economy
- Excessive smoke from exhaust on startup
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data to confirm P068E.
Step 2: Visually inspect the glow plug wiring and connector for cylinder 8 for damage, corrosion, or loose connections.
Step 3: Measure resistance of the cylinder 8 glow plug; compare to manufacturer specs (typically 0.5-2 ohms).
Step 4: Check voltage at the glow plug connector with key on; should be battery voltage (12V). If low, trace circuit back to control module.
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, especially in cold weather, as it can cause hard starting, misfires, and potential damage to the catalytic converter due to unburned fuel.
How much does it cost to fix?▼
The cost to fix P068E typically ranges from $50 to $150, including parts and labor. A single glow plug replacement is usually under $100, but if the control module or wiring needs repair, costs may be higher.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.