U0106

Lost Communication With Glow Plug Control Module

Car Fault Codes Network

Can you still drive? Yes, normally

Who can fix it? Needs a workshop

Typical repair time 30 minutes – 3 hours

Typical cost SAR 100 to 2,500

What it means

The engine computer (ECU) has stopped receiving messages from the glow plug control module over the network. This module exists on diesel engines and heats the combustion chambers to make cold starts easier, so starting can be hard in cold weather while symptoms are mild in hot weather. The cause is usually module power, its connector or the bus wiring, and several U codes together point to a bus or power problem.

Symptoms5

Hard starting when the engine is cold, especially in winter.
White smoke on a cold start until the engine warms up.
Glow plug light or check engine light flashing or on.
Rough running in the first minutes after starting.
Scan tool cannot communicate with the glow plug module.

Possible causes6

Blown module power fuse, which may be a large fuse because glow plugs draw high current.
Module connector corroded by water or engine heat.
Weak battery or loose terminals.
Poor module ground.
Open or shorted communication wiring to the module.
Internal module failure, sometimes after a shorted glow plug.

How to diagnose5

Read codes from all modules; if many modules report lost communication, start with the battery and the bus, and if only the glow plug control module is missing, focus on it.
Try to communicate with the glow plug control module directly with a scan tool; no response points to lost power, ground or wiring to it.
Locate the glow plug control module from the manufacturer information, which exists only on diesel engines, and its location varies by make, then check its power fuse and measure power and ground at its connector.
Inspect the module connector for water, corrosion or loose terminals, and check the bus wiring to it.
Disconnect the battery and measure resistance between the CAN bus wires at the module connector, comparing with the manufacturer specification to find an open or short.

How to fix6

Charge or replace the battery, and clean and tighten its terminals.
Replace the blown fuse after finding why it blew.
Clean the module connector and repair the ground or damaged bus wiring.
Update the module software if the manufacturer has an update.
Replace the glow plug control module if proven faulty with good power and bus wiring, then program and code it to the vehicle.
Clear codes in all modules and confirm the code does not return.

Repair cost

0–500

500–2,000

2,000–5,000

5,000+

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low for a fuse or connector, rises if the module must be replaced, and the cost of damaged glow plugs may be added if they caused the failure.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions

Why don't I notice symptoms in summer?

A diesel engine ignites easily in hot weather without extra heating, so the symptoms of this code show up more in cold weather.

Should the glow plugs be checked too?

Yes. A shorted glow plug can damage the module, so check the plugs before fitting a new module so it is not damaged again.

Can I drive with this code?

Usually yes, since the engine runs once started, but fix it soon to avoid hard starting, smoke and extra strain on the battery and starter.

Was this explanation helpful?

Tap the stars to rate; you can change it later.

This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.

Report a mistake

Spotted something inaccurate? Tell us and we will review and correct it.