P1399
Glow Plug Circuit High Side, High Input
Severity
⚠️ MediumCan you drive?
Yes, but get it checked soon
Approx. repair cost
$17–89 (est.)
Symptoms
- Difficulty starting the engine (especially in cold weather)
- Check Engine Light Is On
- Reduced engine power
- Increased fuel consumption
- Unstable operation at idle
Causes
- Short circuit in glow plug circuit
- Faulty glow plug relay
- Damaged wiring or poor contacts
- Problems with the glow plug control module
- Faulty Engine Control Unit (ECU)
How to Fix
- Check glow plug circuit fuses
- Check glow plug relay for short circuit
- Inspect the wiring harness for damage
- Check the resistance of the glow plugs
- Check the operation of the glow plug control module or ECU