What it means
A control module has lost communication with the glow plug control module. Glow plug operation may be affected on applicable diesel vehicles.
How it works
The glow plug control module manages glow plug operation to help a diesel engine start when cold. This code sets when another module stops receiving expected messages from it, which can prevent normal preheating and make cold starts difficult.
Common causes
Most likely first.
- Loss of module power or ground
- Open, shorted, or damaged communication wiring or connector
- Module or gateway fault
Symptoms
- Glow plug warning or message
- Hard starting when cold
- Communication faults in other modules
How to diagnose it
- Scan all modules for U011C and glow plug or starting codes, noting which modules report no communication with the glow plug control module.
- Review freeze-frame data and whether the starting problem occurs mainly when the engine is cold.
- Inspect the module connector, glow plug harness, and nearby wiring for corrosion, heat damage, loose connections, or chafing.
- Check the module's power and ground circuits against the manufacturer's specification.
- Test the communication wiring to the glow plug control module for opens, shorts, or poor connections.
- If supplies and network wiring pass, diagnose the module and gateway with vehicle-specific procedures.
Common fixes
- Clean or repair a corroded connector or damaged glow plug module harness.
- Restore a failed power feed or ground to the glow plug control module.
- Repair an open or short in the module's communication wiring.
- Replace and configure the glow plug control module if its failure is confirmed after circuit checks.
Can I keep driving?
The vehicle may still run, but cold starting can become difficult and repeated cranking can drain the battery or strain the starter. Avoid relying on it for cold starts until the glow plug control 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.