U0108 — Lost Communication With Alternative Fuel Control Module

Is it safe to drive with U0108?

Depends on what is affected. A single dead convenience module is fine to drive with; loss of communication with engine, braking or steering modules is not. If multiple critical systems drop out, do not drive.

What are the symptoms of U0108?

Drivers most often notice: random, hard-to-reproduce electrical glitches, modules intermittently not communicating with the scanner, multiple warning lights on at once, intermittent loss of functions (gauges, windows, steering assist).

How much does it cost to fix U0108?

Repair CAN wiring or connectors — $100–$400; Replace the faulty control module — $300–$1,500; Remove interfering aftermarket device — $0–$150. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Will U0108 clear itself?

Sometimes U0108 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What does OBD2 code U0108 mean?

OBD2 code U0108 flags a problem with the vehicle network (CAN bus) communication (lost communication with alternative fuel control module). Short, gentle driving to a shop is usually possible. Common culprits: corroded connectors, especially in wet areas, poor grounds or low battery voltage, damaged CAN bus wiring or short to power/ground.

What does U0108 mean?

U0108 is logged by the onboard diagnostics when the vehicle network (CAN bus) communication does not behave as expected. The official definition is “Lost Communication With Alternative Fuel Control Module”. This is a vehicle network category code.

The module monitors this system continuously while driving. When readings fall outside the expected range for a defined number of drive cycles, it stores U0108 and switches on the warning light. Freeze frame data saved with the code shows the exact conditions — rpm, load, temperature, speed — at the moment the fault was detected, which is the best starting point for diagnosis.

What causes U0108?

• water ingress in harness junctions
• aftermarket equipment interfering with the bus
• corroded connectors, especially in wet areas
• poor grounds or low battery voltage

Common symptoms of U0108

• random, hard-to-reproduce electrical glitches
• modules intermittently not communicating with the scanner
• multiple warning lights on at once
• intermittent loss of functions (gauges, windows, steering assist)
• no-start or intermittent starting in some cases

How to diagnose U0108

1. Connect an OBD2 scanner, confirm U0108 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
2. Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many U0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
3. Visually inspect the wiring harness and connectors related to the vehicle network (CAN bus) communication for damage, corrosion, chafing or poor contact.
4. Measure resistance between CAN-High and CAN-Low at the OBD port with power off — about 60 Ω is healthy.
5. Scan all modules: the one that does not respond is either the culprit or downstream of the break.
6. Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm U0108 does not return.

How to fix U0108

Start with the cheapest and most common causes before replacing expensive parts:

• Repair CAN wiring or connectors — $100–$400
• Replace the faulty control module — $300–$1,500
• Remove interfering aftermarket device — $0–$150

How much does it cost to fix U0108?

Repair cost depends on which component actually failed. Typical scenarios for U0108 (parts and labor, USD, independent shop rates):

• Repair CAN wiring or connectors: $100–$400
• Replace the faulty control module: $300–$1,500
• Remove interfering aftermarket device: $0–$150

Overall, fixing U0108 usually costs between $0 and $1,500. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Can you drive with U0108?

Depends on what is affected. A single dead convenience module is fine to drive with; loss of communication with engine, braking or steering modules is not. If multiple critical systems drop out, do not drive.

Related OBD2 codes

• U0100: Lost Communication With ECM/PCM "A"
• U0101: Lost Communication with TCM
• U0102: Lost Communication with Transfer Case Control Module
• U0103: Lost Communication With Gear Shift Module
• U0104: Lost Communication With Cruise Control Module
• U0105: Lost Communication With Fuel Injector Control Module