U0645Lost Communication With Active Air Dam Module
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- An active air dam is a motor-driven panel below the front bumper that drops at highway speed to cut drag and retracts for low speed or rough ground. Its small control module talks to the powertrain controller over a serial line; on the 2.7L F-150 Ford runs it on a LIN bus shared with the generator and the grille shutters. U0645 is logged once that module no longer replies. Ram uses it on the 1500 DT: TSB 23-029-22 covers 2019 trucks built up to 21 January 2019 (sales code MXB) with the MIL lit, and a new air dam under an eight-year warranty extension. A 2025 Ram case asks for impact damage, connector corrosion and resistance checks first. Ford's SSM 50737 blames a LIN wire grounded at the left engine mount. Actuator faults are C0601 to C0630.
- What you may notice
- Air dam stays in one position
- Check engine light on some trucks (Ram)
- Charging system warning if the shared LIN line is shorted (Ford)
- Likely causes
- LikelyAir dam unit with built-in module failed (early Ram 1500 DT)
- PossibleAir dam damaged by curb, snow or debris impact
- PossibleWater or corrosion in the air dam connector
- RareShared LIN wire chafed to ground near the engine mount (Ford F-150 2.7L)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €40 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.