What it means
The control line for the glow plug on cylinder 7 is open or shorted to supply - the plug cannot be heated.
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 the cylinder 7 control circuit, and P068D sets when that circuit reads high, which can indicate an open plug or wire or a short to supply that prevents heating.
Common causes
Most likely first.
- Open in plug or wiring
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
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 confirm whether cylinder 7 is the only affected circuit.
- Inspect the cylinder 7 glow plug connector and wiring for a loose or corroded terminal, broken wire, or contact with a power source.
- Compare the cylinder 7 circuit reading with other glow plug circuits using the manufacturer’s diagnostic procedure.
- Test the cylinder 7 plug and wiring for an open circuit or short to supply, following the manufacturer’s specifications.
- If the plug and wiring pass, test the glow plug controller’s cylinder 7 output before considering a controller fault.
Common fixes
- Repair an open or damaged cylinder 7 glow plug wire.
- Repair a wire shorted to supply or correct damaged insulation.
- Clean or repair a loose or corroded cylinder 7 connector.
- 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 engine may run normally once warm, but a cylinder 7 glow plug that cannot heat can make cold starts difficult and cause white smoke during warm-up. Avoid repeated long cranking in cold weather because it 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.