U0108

Lost Communication With Alternative Fuel Control Module

Car Fault Codes Network

Can you still drive? Yes, normally

Who can fix it? Needs a workshop

Typical repair time 30 minutes – 4 hours

Typical cost SAR 100 to 3,000

What it means

The engine computer (ECU) or another module has stopped receiving messages from the alternative fuel control module over the network. This module exists on vehicles running on natural gas or liquefied petroleum gas, and when communication is lost the vehicle usually switches back to gasoline or cannot use gas. The cause is usually module power, its connector or the communication wiring, and the problem is more common with poorly installed conversion systems.

Symptoms5

Vehicle switches to gasoline and cannot run on gas.
Check engine light or gas system light on.
Gas level indicator or fuel selector switch not working.
Stumbling or hesitation when trying to switch to gas in some cases.
Scan tool cannot communicate with the alternative fuel module.

Possible causes6

Poor electrical connections in aftermarket conversion systems.
Blown module power fuse.
Corroded or loose module connector in the engine bay.
Weak battery or poor ground.
Open or shorted communication wiring to the module.
Internal module failure or software not compatible with the engine computer.

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 alternative fuel control module is missing, focus on it.
Try to communicate with the alternative fuel control module directly with a scan tool; no response points to lost power, ground or wiring to it.
Locate the alternative fuel control module from the manufacturer information, which exists only on vehicles running on natural gas or liquefied petroleum gas, factory-fitted or converted, and its location varies by system, 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 alternative fuel 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 conversion system wiring needs rework, and is highest if the module must be replaced and programmed.

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

Does this code appear on regular vehicles?

No. It concerns vehicles equipped with a natural gas or liquefied petroleum gas system, factory-fitted or converted.

Can I drive with this code?

Usually yes, on gasoline, but have it repaired at a workshop that specializes in gas systems, and do not tamper with gas components yourself.

Why does the code keep coming back on converted vehicles?

Conversion wiring is sometimes connected temporarily or without good insulation, so it is affected by heat and moisture over time.

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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.

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