What it means
The PCM has detected a fault in the communication circuit with the glow plug control module. This can interfere with glow plug control.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The glow plug control module manages power to the engine's glow plugs, while the PCM communicates with it to request and monitor glow plug operation. This code sets when the PCM detects a fault in that communication link, so glow plug control may be interrupted even if the individual plugs are intact.
Common causes
Most likely first.
- Communication wiring or connector fault
- Glow plug control module fault
- PCM fault
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
- Record freeze-frame data and scan for related PCM and glow plug control module codes to determine whether the communication fault is persistent or intermittent.
- Inspect the communication wiring and connectors between the PCM and glow plug control module for corrosion, loose pins, damage, or chafing.
- Check the module's power and ground connections, since a supply or ground fault can interrupt communication.
- Test the communication circuit for opens, shorts, or poor connections using the manufacturer's wiring diagram and procedure.
- If wiring, power, and ground are sound, verify the glow plug control module and PCM communication functions using the manufacturer's diagnostic steps.
Common fixes
- Clean and secure corroded or loose communication-circuit connector pins.
- Repair damaged, open, or shorted wiring between the PCM and glow plug control module.
- Restore faulty power or ground connections at the glow plug control module.
- Replace the glow plug control module if it fails the manufacturer's communication tests.
- Repair or replace the PCM only if its communication circuit is confirmed faulty.
Can I keep driving?
If the engine runs normally, driving may be possible, but cold starting can become difficult and warm-up smoke may increase if glow plug operation is lost. Avoid repeated long cranking; arrange prompt diagnosis if the engine struggles to start or stalls.
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.