P06FD
Glow Plug Control Module 2 to PCM Communication Circuit Range/Performance.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 6
- AreaComputer and output circuits
- FD
- FaultThe specific fault in that area
What it means
P06FD is a generic code meaning the powertrain control module has detected a range or performance problem on the communication circuit between itself and glow plug control module 2. The PCM expected valid, plausible data from the module but received signals that were out of range, corrupted, intermittent or not behaving as expected. The exact circuit type and the number of glow plug modules fitted vary by model and engine, so check manufacturer data.
Symptoms
- Glow plug or engine management warning light on
- Hard starting or extended cranking in cold weather
- White smoke and rough running on a cold start
- Rough idle or misfire until the engine warms up
- Poor cold-weather performance or reduced power
- Other communication or glow plug codes stored alongside
Possible causes
- Damaged, chafed or corroded wiring in the communication circuit between the PCM and glow plug control module 2likely
- Poor connection at the glow plug control module or PCM connector (corrosion, loose or spread terminals, water ingress)likely
- Low battery voltage or a poor power or earth supply to the glow plug control module causing unstable communicationpossible
- Faulty glow plug control module 2 with an internal communication faultpossible
- Electrical interference or a fault elsewhere on the vehicle network affecting the signalpossible
- Outdated or faulty PCM software or calibration (model-specific, only if a manufacturer bulletin confirms it)rare
- Internal PCM fault in the communication driverrare
How to diagnose
- Read all stored codes and freeze frame data, noting whether the fault is current or intermittent and whether other glow plug or network codes are present
- Check battery condition and charging voltage, as low voltage can upset module communication
- Visually inspect the wiring and connectors for glow plug control module 2 and the PCM for chafing, heat damage, corrosion, water ingress and loose terminals
- Check the power supply, fuses and earth connections to glow plug control module 2 against the wiring diagram
- Wiggle-test the harness with the engine running or the live data displayed to see if the fault appears or communication drops
- Test the communication circuit for continuity, short to earth, short to voltage and resistance against manufacturer specifications
- Check the live data for the glow plug module status and compare with the PCM commands, following the manufacturer procedure for your model
- Check for software updates or technical bulletins for your model before condemning the module or PCM
How to fix
- Repair or replace damaged wiring in the communication circuit and secure the harness away from heat and abrasion
- Clean, repair or replace corroded or damaged connectors and terminals
- Correct battery, power supply or earth faults affecting the glow plug control module
- Replace glow plug control module 2 if testing confirms an internal fault, and code or adapt it as the manufacturer requires
- Update the PCM software only if a manufacturer update addresses this fault
- Repair or replace the PCM only after wiring, supply and module faults have been ruled out
Can I keep driving?
The car can usually be driven short-term, but cold starting may be poor and the fault could worsen, so have it fixed soon. Avoid repeated cold starts if the engine runs very roughly or smokes heavily.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.