What it means
The control module has detected an incorrect condition in the cylinder 12 glow plug circuit. The code does not by itself establish that the wrong plug type was fitted.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The cylinder 12 glow plug provides heat in that cylinder to help a diesel engine start and combust fuel cleanly when cold. The control module monitors the cylinder 12 plug circuit and sets this code when its electrical response is incorrect; it does not by itself establish that the plug type is wrong.
Common causes
Most likely first.
- Faulty glow plug
- Damaged or corroded wiring or connector
- Glow plug control circuit fault
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
- Check freeze-frame data and related glow-plug codes to see when the cylinder 12 fault appeared and whether other cylinders are affected.
- Inspect the cylinder 12 plug connector and harness for corrosion, looseness, damaged insulation, or heat exposure.
- Measure the cylinder 12 glow plug's resistance or current draw against the manufacturer's specification and compare it with other plugs.
- Use the wiring diagram to test the cylinder 12 branch for continuity and shorts between the plug and control circuit.
- If the plug and branch wiring are sound, test the controller's cylinder 12 output according to the manufacturer's procedure.
Common fixes
- Clean and reseat the cylinder 12 glow plug connector.
- Repair damaged or corroded wiring in the cylinder 12 branch.
- Replace the cylinder 12 glow plug if its test result is outside specification.
- Repair the glow-plug control circuit if the controller output or circuit connection fails testing.
Can I keep driving?
If it starts and runs smoothly, short-term cautious driving may be possible, but cold starts and warm-up emissions can worsen. Avoid prolonged cranking if it will not start, and repair the fault before depending on the vehicle in cold weather.
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.