What it means
The control line for the glow plug on cylinder 7 is shorted to ground or the plug is internally shorted.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The glow plug on cylinder 7 heats that cylinder’s combustion chamber to support diesel starting in cold conditions. The glow plug controller monitors its cylinder 7 control circuit, and P068C sets when that circuit is low, commonly because it is shorted to ground or the plug itself is internally shorted.
Common causes
Most likely first.
- Control line shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Glow plug warning light on (often orange coil symbol)
- Hard cold start or no start in cold weather
- White smoke from exhaust during warm-up
How to diagnose it
- Record freeze-frame data and check for other glow-plug codes to determine whether the fault is limited to cylinder 7.
- Inspect the cylinder 7 glow plug connector and the wiring along its route for corrosion, loose terminals, or insulation chafed through to ground.
- Compare the cylinder 7 circuit reading with other glow plug circuits using the manufacturer’s diagnostic procedure.
- Test the cylinder 7 glow plug and its control wire for a short to ground, following the manufacturer’s procedure.
- If the plug and wiring pass, test the glow plug controller’s cylinder 7 output before considering a controller fault.
Common fixes
- Repair cylinder 7 wiring shorted to ground.
- Clean or repair corroded or loose cylinder 7 connector terminals.
- Replace the cylinder 7 glow plug if it fails the specified test.
- Replace the glow plug controller only if its cylinder 7 output fails testing with sound wiring and plug.
Can I keep driving?
The vehicle may start and run in mild weather, but cold starts can become difficult and unburned fuel may produce white smoke during warm-up. Avoid repeated long cranking in cold conditions, which can drain the battery and stress the starter.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.