What it means
Glow Plug Control Module 2 to PCM Communication Circuit: an electrical fault is present in the circuit. This affects diesel cold-start preheating.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Glow Plug Control Module 2 manages preheating for the diesel engine’s glow plugs and communicates its status to the PCM. The PCM sets P06FC when it detects an electrical fault in the communication circuit between the two modules, such as an open or short.
Common causes
Most likely first.
- Open or short on communication wire
- Gateway module routing CAN messages incorrectly
- CAN terminating resistor (120 Ω) drifted out of spec
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
- Read freeze-frame data and all PCM and network codes to see when communication with Glow Plug Control Module 2 was lost and whether other modules report network faults.
- Check the glow plug warning light and cold-start symptoms, and note whether the fault is present continuously or intermittently.
- Inspect the wiring and connectors between Glow Plug Control Module 2 and the PCM for damage, corrosion, loose pins, or poor contact.
- With the wiring diagram, test the communication circuit for continuity and shorts to power or ground, following the manufacturer's procedure.
- If the wiring checks out, check gateway routing and CAN network integrity, including termination against the manufacturer's specification, before suspecting either module.
Common fixes
- Clean and secure corroded or loose communication-circuit connectors.
- Repair an open, shorted, or damaged wire between Glow Plug Control Module 2 and the PCM.
- Correct a gateway routing fault if network diagnosis confirms it.
- Repair or replace a CAN terminating resistor if it is out of the manufacturer's specification.
- Replace a module only after its power, ground, wiring, and network communication have been verified.
Can I keep driving?
If the engine starts and runs normally, a short trip may be possible, but avoid relying on the vehicle for cold starts until the fault is diagnosed. In cold weather, failed preheating can cause hard starting or a no-start, and incomplete combustion may produce white smoke during warm-up.
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.