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DTC codes / U01xx · Lost communication with a control module / U0106

U0106Lost Communication With Glow Plug Control Module

U0106 is a generic network communication code indicating that the engine control module has lost the controller area network messages it expects from the glow plug control module. The engine computer detects this when the glow plug module stops broadcasting its periodic status frames or fails to acknowledge requests over the communication bus.

SystemNetwork
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaLost communication with a control module

Symptoms you may notice

  • Illuminated check engine light or service vehicle soon message with no other obvious change in driving behavior
  • Hard cold starting or extended cranking before the engine fires, especially in low ambient temperatures
  • A glow plug warning lamp or message displayed in the instrument cluster on diesel vehicles
  • Rough idle and white exhaust smoke immediately after a cold start
  • Reduced engine power or a limp-home strategy triggered by the missing module data
  • Often no symptoms besides the warning light when the fault is intermittent or ambient temperatures are warm

Common causes, most likely first

  1. Corroded, loose, or backed-out terminals in the glow plug control module connector
  2. Open or shorted wiring in the controller area network bus pair between the engine control module and the glow plug module
  3. Failed glow plug control module, often from internal water intrusion or heat damage
  4. Blown fuse or missing power and ground feeds to the glow plug control module
  5. A second module on the same bus segment pulling the network down and disrupting communication
  6. Low battery voltage or poor chassis grounds causing intermittent module dropouts

How to diagnose and fix it

  1. Scan all modules for communication codes and record which modules are online to confirm the glow plug module is truly offline
  2. Inspect the glow plug control module connector for corrosion, pushed pins, and water intrusion, then clean and reseat it
  3. Check the module's power and ground circuits with a multimeter and verify any dedicated fuse is intact
  4. Measure resistance and voltage on the controller area network bus pair at the module connector to rule out an open or short
  5. Perform a voltage drop test on grounds and battery feeds while cranking to catch intermittent supply faults
  6. Substitute a known-good glow plug control module or perform a bidirectional communication test to confirm the module itself has failed
  7. Clear the code and road test through several key cycles to verify the communication loss does not return

Why the glow plug module goes silent

  • A glow plug module that communicates perfectly on a warm engine but drops off in freezing weather often has an internal solder joint or water intrusion fault that only appears under thermal contraction.
  • Technicians frequently replace the glow plug module when the real culprit is a chafed bus wire behind the engine block or a corroded ground that also feeds other modules on the same segment.
  • U0106 can be stored by a completely different module on the network that is shorting the bus, so always check whether other communication codes accompany it before condemning the glow plug controller.
  • On some vehicles the glow plug control module shares a fuse or relay with the cooling fan or secondary air pump, so a blown shared fuse will kill communication without any obvious glow plug symptom.
  • A weak battery that drops below the module's minimum operating voltage during cranking can set U0106 intermittently, and the code will keep returning until the battery and charging system are verified.

Can I keep driving with U0106?

The vehicle will usually start and run, but cold-start performance and emissions control may be compromised, so avoid prolonged driving in freezing conditions until the fault is repaired. If the engine enters a reduced-power limp mode, limit driving to a short trip to a repair facility.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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