U0106: Lost Communication With Glow Plug Control Module 1
What to do
In mild weather you will probably notice nothing. In cold weather expect slow starting, white smoke for the first minute and rough running until the engine warms.
That seasonal pattern is the thing to be aware of: a car that starts fine today can be a car that will not start on the first frost, so this is worth dealing with before winter rather than after. It is also not a reason to replace glow plugs — the plugs may be perfectly good, and the module that operates them has simply stopped receiving instructions.
What this code means
The glow plug control module has stopped being heard from. The general reasoning is at U0100, and the module's own communication faults are at P0683 and P0684.
Glow plugs are controlled by a dedicated module because they draw large currents on a timed schedule that varies with temperature — and because the module measures each plug individually, which is what allows a single failed plug to be identified rather than a set replaced.
Losing communication with it means the engine module cannot ask for preheat, so on a cold morning the plugs may not operate at all. The symptom is therefore seasonal and easy to misread: in mild weather the car starts perfectly and nothing seems wrong, and the fault only becomes obvious when the temperature drops. A code stored in summer is a problem stored up for winter.
These modules sit in the engine bay carrying heavy current, so heat and corrosion at their connectors are ordinary findings.
Likely causes
Start here
- Corroded or loose connector · easy
- Damaged data bus wiring · moderate
- Failed power or earth supply to the module · moderate
Less common
- Heat damage to sensor or wiring · moderate
- Failed glow plug control module · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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