Lost Communication With Glow Plug Control Module
Your engine's computer lost contact with the glow plug control module, like a walkie-talkie losing signal between two devices. This prevents the glow plugs from warming up properly before diesel engine startup.
The ECM communicates with the glow plug control module via a serial data bus (CAN/LIN) to verify module presence and command glow plug heating cycles. The ECM monitors for valid communication signals within a specific timeout window during startup. If the module fails to respond or acknowledge commands within the expected timeframe, a communication loss is flagged.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Bus Communication Response Time | < 100 milliseconds per command | > 500 milliseconds or no response |
| Module Heartbeat Signal | Present every 1-2 seconds | Missing for > 3 seconds |
Code U0106 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, U0106 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.