U0106Generic code

U0106 Code: Lost Communication with Glow Plug Control Module

The U0106 code means other modules in the vehicle stopped receiving messages from the glow plug control module. The usual effect is hard starting when the engine is cold. It is a low severity code and you can keep driving, but cold starts may be rough.

Severity
Low
Can I keep driving?
Yes, no immediate risk
Estimated cost
$0 to $1,500
Difficulty
Medium
System
Communication Network
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

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What the U0106 code means

The modules in the vehicle exchange information constantly over the data network, normally CAN. The glow plug control module controls the glow plugs on a diesel engine. When the other modules stop receiving its messages for a while, they log the U0106 code.

The code is stored by the module that misses the information, not by the one that is failing. That is why it often shows up in several modules at once. The problem can be in the glow plug control module itself (no power, no ground or failed), in its connector or in the network wiring that reaches it.

Usual location: in the engine bay or under the vehicle. If that area is exposed to water or was recently repaired, start there.

Work the diagnosis in this order: 1) battery and alternator, because low system voltage is the number one cause of bursts of U codes; 2) the module list on the scan tool, to see which module is not responding; 3) power, fuses and grounds of the module that is not responding; 4) network resistance at the OBD2 connector, about 60 ohms between pins 6 and 14 with the battery disconnected; 5) connectors and wiring at the module, especially in areas exposed to moisture such as under the carpets, in the doors and in the trunk.

Measuring the network and isolating the module that is bringing it down is the heart of any U code diagnosis, so take the time to do those steps in order before you replace anything.

U0106 code symptoms

  • Warning lights on the dash.
  • Hard starting when the engine is cold.
  • Communication codes in several modules at the same time.
  • The fault can be intermittent, for example in the rain or over bumps.

Likely causes of the U0106 code

  1. Module power or ground: a blown fuse, a corroded ground or a loose power connector.
  2. Weak battery or low voltage: it makes modules reboot and lose communication.
  3. Module connector with water or corrosion: very common for modules located in wet areas.
  4. Damaged network wiring: CAN high or CAN low cut or shorted.
  5. Failed glow plug control module: only after ruling out everything above.
  6. Poorly installed accessory: alarms or trackers wired into the network.

How to diagnose the U0106 code step by step

  1. Measure the battery voltage at rest (12.4 to 12.7 V) and with the engine running (13.5 to 14.7 V).
  2. Check on the scan tool which modules respond. If the glow plug control module does not show up, the fault is in the module or in its connection.
  3. Check the module fuses and grounds using the wiring diagram.
  4. Measure the network at the OBD2 connector. You should see about 60 ohms between pins 6 and 14 with the battery disconnected, and roughly 2.5 V on each wire with the key on.
  5. Inspect the module connector for moisture, corrosion and bent pins.
  6. Measure CAN high and CAN low at the module connector. They should have continuity with the OBD2 connector.

How to fix the U0106 code

  • Repair the module power, ground or connector.
  • Repair the network wiring.
  • Replace and program the module if it has failed, which almost always requires programming.
  • Clear the codes in all modules and verify.

Technical reference data

  • CAN network resistance between OBD2 pins 6 and 14: about 60 ohms.
  • CAN high: 2.5 to 3.5 V. CAN low: 1.5 to 2.5 V.
  • These values are a guide only, so check the manufacturer data for your vehicle.

Brand-specific notes

After you fix the U0106 code, clear the codes in all modules. Many of them keep old U codes from the time the fault was present. Accessories installed after the sale, such as alarms, GPS trackers and OBD2 adapters left plugged in permanently, are a frequent cause of network problems.

Frequently asked questions about U0106

Can I drive with a U0106 code?
Yes, in general. The functions of that module, such as glow plug control for cold starts, may not be available.
Does U0106 mean the glow plug control module is bad?
Not necessarily. The most frequent cause is its power, its ground, its connector or the battery.
Why do so many codes show up at once?
Because every module that was waiting for information from the affected module logs the fault.
How much does it cost to fix U0106?
Between $0, if it was the battery or a fuse, and $1,500 if the module has to be replaced and programmed.
What does the U0106 code mean?
It is a generic OBD2 code that means other modules lost communication with the glow plug control module. The code does not say which part of the circuit has the fault.
Will a U0106 code clear itself?
Only if the cause was temporary, such as a low battery that was recharged. If a connector, a ground or the module is at fault, the code comes back.
What is the most common cause of U0106?
Power or ground problems at the module, a weak battery or a connector with water or corrosion. A failed module is the last thing to suspect.

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