U0106
Lost Communication With Glow Plug Control Module 1
Communication network (diesel start aid)
Generic OBD-II
Medium
What it means
U0106 means the engine computer has lost communication with the glow plug control module, the unit that preheats a diesel's cylinders for starting. Without it, cold starts become hard or impossible and the engine may smoke and run rough while warming up. A warm engine usually still starts and runs, but the cold-start aid is out until the wiring, power, or module is repaired.
Medium
Can I keep driving? You can usually drive once warm, but expect hard cold starts and possibly rough running or white smoke until the glow plug system is restored.
Common symptoms
What you'll notice
- Hard or extended cranking when starting cold
- Glow plug (wait-to-start) or check-engine light on
- Rough running and white smoke right after a cold start
- Glow plug control module missing when scanned
Common causes
Most likely first
- Open, shorted, or chafed wiring to the glow plug control moduleLikely
- Corroded or loose connector at the moduleCommon
- Blown fuse or lost power/ground feed to the moduleCommon
- Failed glow plug control moduleLess often
- Bus fault upstream preventing the module from reportingLess often
How to diagnose & fix
Work through it in order
- Scan all modules and confirm the glow plug module is unreachable.
- Check the module's power, ground, and fuse feeds.
- Inspect the wiring and connector at the glow plug control module for damage or corrosion.
- Check the CAN bus lines to the module for open/short against the wiring diagram.
- If wiring and power are good, replace the glow plug control module, clear the code, and retest a cold start.
FAQ
Quick answers
Is it safe to drive with U0106?+
The engine runs, but cold starts will be hard and it may smoke and run rough while warming up. On a diesel in cold weather it can become a no-start, so fix it before winter.
Can I just clear U0106?+
It returns as soon as the module stays offline. The wiring, power feed, or module has to be repaired.
Related codes
Often seen with U0106
Read & clear U0106 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX