What it means
The drive line from the PCM to glow plug control module 1 is stuck high — short to B+. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The PCM sends a control signal to glow plug control module 1, which manages the glow plugs that warm a diesel engine for cold starting. This code sets when the PCM detects that the module’s control circuit is held at a higher voltage than expected, such as from a short to battery power.
Common causes
Most likely first.
- Short to B+
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
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
- Check freeze-frame data and glow plug live data to see whether the fault occurred during a cold start and whether module 1 responds to a glow request.
- Inspect the module 1 connector and the PCM-to-module control wire for water, corrosion, pushed-back pins, chafing, or contact with a power feed.
- With the circuit active, move the accessible harness gently and watch the scan data for a change that could locate an intermittent short.
- Use the wiring diagram to test the control wire for an unintended connection to battery positive, following the manufacturer's procedure.
- If the wiring and connectors pass, check module 1 and the PCM control output according to the manufacturer's diagnostic procedure.
Common fixes
- Repair chafed or pinched control wiring that is contacting a power source.
- Clean or repair corroded connectors and restore any pushed-back pins.
- Replace a confirmed faulty glow plug control module 1.
- Repair a confirmed PCM control-output fault.
Can I keep driving?
A warm engine may still start and run normally, but cold starts can become difficult and produce white smoke. Avoid repeated long cranking in cold weather; if the engine will not start reliably, arrange repair before relying on it.
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.