Open or shorted communication wire between glow plug control module 2 and the PCM; Corroded, loose, or pushed-back terminal in the module or PCM connector; Failed glow plug control module 2 internal communication circuit; PCM internal fault on the communication driver or receiver; Chafed harness or damaged connector caused by heat, vibration, or rodent activity; Poor ground or power feed to glow plug control module 2 causing it to drop offline; Aftermarket electrical accessories or poor prior repairs disturbing the circuit

DTC codes / P06xx · Computer and output circuits / P06FC

P06FCGlow Plug Control Module 2 to PCM Communication Circuit

Q: What does code P06FC mean?

Glow Plug Control Module 2 to PCM Communication Circuit. P06FC means the powertrain control module (PCM) has lost or detected an invalid communication signal on the dedicated circuit linking it to glow plug control module 2. The PCM monitors this circuit for expected voltage or message activity and sets the code when the signal is missing, out of range, or implausible for a calibrated amount of time.

P06FC means the powertrain control module (PCM) has lost or detected an invalid communication signal on the dedicated circuit linking it to glow plug control module 2. The PCM monitors this circuit for expected voltage or message activity and sets the code when the signal is missing, out of range, or implausible for a calibrated amount of time.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyProfessional

AreaComputer and output circuits

Symptoms you may notice

Illuminated check engine light or glow plug warning lamp, often with no other symptoms
Hard cold starting or extended cranking before the engine fires
Rough idle and white exhaust smoke immediately after a cold start
Reduced engine power or limp mode in some vehicles
Glow plug monitor or readiness status not completing during inspection
No noticeable drivability change once the engine is warm

Common causes, most likely first

Open or shorted communication wire between glow plug control module 2 and the PCM
Corroded, loose, or pushed-back terminal in the module or PCM connector
Failed glow plug control module 2 internal communication circuit
PCM internal fault on the communication driver or receiver
Chafed harness or damaged connector caused by heat, vibration, or rodent activity
Poor ground or power feed to glow plug control module 2 causing it to drop offline
Aftermarket electrical accessories or poor prior repairs disturbing the circuit

How to diagnose and fix it

Scan all modules and record every stored and pending code before clearing anything
Inspect the glow plug control module 2 connectors and PCM connectors for corrosion, loose pins, or pushed-back terminals
Check the module's power and ground feeds with a multimeter and verify they are within specification
Perform a voltage-drop and continuity test on the communication circuit between the module and PCM
Wiggle-test the harness while watching live communication status or a scope to expose intermittent faults
If the circuit tests good, substitute a known-good glow plug control module 2 and recheck communication
If communication returns only with a replacement PCM, program and adapt the new PCM to the vehicle

What the communication circuit code hides

A failed glow plug control module 2 can set this code without any glow plug fault codes, so technicians who only scan for glow plug circuit codes miss the real problem.
The communication circuit is often a low-current signal wire, and a poor ground at the module can corrupt that signal even when the wire itself tests continuous.
Intermittent P06FC is frequently caused by heat-soaked connectors near the engine, so the fault may only appear after the engine reaches operating temperature.
Replacing the PCM first is a common and expensive misdiagnosis; the module, its power feed, and its ground should be ruled out before condemning the PCM.
Some vehicles set P06FC when battery voltage is low during cranking, so a weak battery or charging system can mimic a communication failure.

Can I keep driving with P06FC?

The vehicle can usually be driven, but cold starting and cold-running emissions may be affected, and some vehicles may enter limp mode. Avoid long periods of cold idling and have the circuit diagnosed before winter or repeated hard starts cause 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.