U0108
Lost Communication With Alternative Fuel Control Module
The ECU has lost CAN communication with the alternative fuel control module (CNG/LPG/H2 systems). Either the module is not responding or the bus path is broken.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Common causes
Ordered by how often each turns out to be the cause.
- Module unpowered or fuse blownCommon
- CAN wiring to module brokenPossible
- Gateway module routing CAN messages incorrectlyLess likely
Parts involved
- Alt Fuel Module
- CAN Bus
U0108 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.