U0108Lost Communication With Alternative Fuel Control Module
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- U0108 covers a separate controller for an alternative fuel such as LPG or CNG, added to an engine that otherwise runs a gasoline control strategy. Roush CleanTech's fourth-generation propane systems for Ford E- and F-Series trucks (2016–2018) are a documented user: the PCM expects CAN traffic from the system's Smart Relay Module and stores U0108 when those messages keep missing. Roush lists broken wiring between SRM and PCM, a blown fuse and lost power or ground at the SRM as causes, rough idle as a symptom. Under CARB rules, every electronic powertrain part that can raise emissions falls under comprehensive component monitoring, which makes the link emission-relevant. U0409 covers implausible data, U0309 a software mismatch.
- What you may notice
- MIL on
- Rough idle or poor running on the alternative fuel
- System may stay on or revert to gasoline
- Likely causes
- LikelyAlternative fuel module without power or ground (fuse, relay)
- PossibleDamaged CAN wiring between conversion module and PCM
- PossibleWater or corrosion in the module connectors
- RareAlternative fuel module internally faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.