Faulty glow plug on cylinder 8 (open or shorted element); Damaged or corroded electrical connector at the glow plug; Chafed or broken wire in the glow plug circuit; Failed glow plug control module or relay; Poor ground connection for the glow plug circuit; ECM software issue or internal fault (rare)

DTC codes / P06xx · Computer and output circuits / P06C0

P06C0Cylinder 8 Glow Plug Circuit Range/Performance

Q: What does code P06C0 mean?

Cylinder 8 Glow Plug Circuit Range/Performance. P06C0 indicates that the engine control module (ECM) has detected an out-of-range or performance fault in the glow plug circuit for cylinder 8, typically on diesel engines. The ECM monitors the circuit's electrical characteristics and compares them to expected values; when the voltage or current falls outside the normal range for a calibrated period, it stores this code.

P06C0 indicates that the engine control module (ECM) has detected an out-of-range or performance fault in the glow plug circuit for cylinder 8, typically on diesel engines. The ECM monitors the circuit's electrical characteristics and compares them to expected values; when the voltage or current falls outside the normal range for a calibrated period, it stores this code.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaComputer and output circuits

Symptoms you may notice

Illumination of the check engine light or glow plug warning light
Hard starting or rough idle when the engine is cold
Excessive white smoke from the exhaust after a cold start
Misfire or rough running during the warm-up phase
Often no symptoms besides the warning light, especially in mild climates

Common causes, most likely first

Faulty glow plug on cylinder 8 (open or shorted element)
Damaged or corroded electrical connector at the glow plug
Chafed or broken wire in the glow plug circuit
Failed glow plug control module or relay
Poor ground connection for the glow plug circuit
ECM software issue or internal fault (rare)

How to diagnose and fix it

Perform a visual inspection of the cylinder 8 glow plug, connector, and wiring for damage or corrosion
Measure the resistance of the glow plug with a multimeter and compare to specifications
Check for battery voltage at the glow plug connector during the glow plug pre-heat phase
Test the glow plug control module and relay for proper operation
Inspect and clean ground connections related to the glow plug circuit
If resistance is out of specification, replace the faulty glow plug
Clear the code and verify the repair by monitoring glow plug operation with a scan tool

Glow Plug Circuit Checks Before Replacement

A glow plug that tests good on resistance can still cause this code if the control module fails to deliver current, so always verify voltage at the plug during activation.
Corrosion inside the glow plug connector is a frequent hidden cause that mimics a failed glow plug, so inspect the terminals closely before condemning the plug.
The code can be set by a weak battery or charging system issue that causes low voltage during glow plug operation, so check battery health first.
On some vehicles, the glow plug control module is integrated into the engine control module, making diagnosis more complex and requiring scan tool data.
Do not overlook aftermarket electrical accessories wired into the glow plug circuit, as they can introduce resistance or voltage drops that trigger this code.

Can I keep driving with P06C0?

You can generally drive the vehicle, but cold starting may be difficult and prolonged driving with a faulty glow plug can lead to excessive smoke and engine wear. Avoid heavy loads or high speeds until the fault is repaired, and address the issue promptly to prevent further damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.