V12 diesel engines use twelve glow plugs. Cylinder 12 is at the rear of the block. The cylinder 12 glow plug circuit delivers high-current power. It includes the glow plug controller, the engine harness, and connectors. The computer monitors the circuit. If resistance rises, it flags a code. Rear wiring is exposed to high engine temps, which can melt or damage harness wires.
Mechanic Glossary
12 Glow Plug Circuit
The wiring and electrical harness path that connects the glow plug controller to the cylinder 12 glow plug on V12 diesel engines.
Frequently Asked Questions
A loose connection on the glow plug terminal, a broken wire in the harness, or a failed driver pin on the controller.
Use a multimeter to check continuity from the controller pin to the cylinder 12 glow plug connector.
No. A bad glow plug has infinite resistance, which triggers a code, but the wiring itself must also be tested.