What it means
A general fault is detected on the first glow plug control module - typically a self-diagnosis flag for an internal driver, supply, or watchdog issue.
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 1 manages the heating elements that warm a diesel engine's combustion chambers for cold starting. The engine controller monitors module 1's self-diagnostic status and sets this code when that module reports an internal driver, supply-monitoring, or watchdog fault.
Common causes
Most likely first.
- Glow plug control module 1 internal fault
- Module power supply or ground problem
- Damaged wiring or connector
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
- Save freeze-frame data and scan the engine and glow plug module for supply, communication, and individual glow-plug codes.
- Note whether the glow plug warning lamp behaves normally and whether hard starting or white exhaust smoke occurs during a cold start.
- Inspect glow plug control module 1's connectors, power, ground, and harness for corrosion, loose terminals, heat damage, or chafing.
- Check the module's supply and ground under load and test its wiring for opens or shorts against the manufacturer's specification.
- If supply and wiring are sound, check the glow plugs and their output circuits for faults that could overload module 1.
- If the external circuits pass and module 1 still reports an internal fault, check for an applicable software update and confirm the module diagnosis.
Common fixes
- Clean and secure module 1's power, ground, and harness connections.
- Repair damaged wiring or connector terminals in the module 1 circuit.
- Replace failed glow plugs or repair their output wiring if tests identify an overload or open circuit.
- Replace glow plug control module 1 if its internal fault remains after the supply and output circuits pass.
Can I keep driving?
In mild weather the engine may still run, but cold starts can become difficult and repeated cranking can drain the battery or strain the starter. Avoid relying on the vehicle in cold conditions until the glow plug fault is repaired.
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.