Cylinder 8 Glow Plug Control Circuit High
The P068F code indicates that the engine control module (ECM) has detected a high voltage condition in the glow plug control circuit for cylinder 8. This typically means the circuit has excessive resistance or a short to voltage, preventing proper glow plug operation. Glow plugs are essential for cold starts in diesel engines, and a fault can cause hard starting, misfires, and increased emissions.
01. Most Common Causes
- Faulty glow plug in cylinder 8
- Open or shorted wiring in the glow plug circuit
- Corroded or damaged connector at the glow plug
- Failed glow plug control module or relay
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: Scan for additional codes and record freeze frame data.
Step 2: Visually inspect the glow plug wiring and connector at cylinder 8 for damage or corrosion.
Step 3: Measure resistance of the glow plug; should be low (0.5-2 ohms). High resistance indicates a bad plug.
Step 4: Check voltage at the glow plug connector with key on; should be battery voltage. If not, test the control module and relay.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances, especially in cold weather, as it can cause hard starting and potential engine damage. Have it diagnosed promptly.
How much does it cost to fix?▼
Typically $50-$150 for a single glow plug replacement, but costs can be higher if wiring or the control module needs repair.