U0439Invalid Data Received From All Terrain Control Module
- Generic OBD-II code · Network
- Can trigger limp mode
- How the car detects it
- U0439 relates to the all terrain control module, which manages drive modes for snow, sand, mud or rock and passes the chosen setting to powertrain, brake and suspension controllers. A receiver sets it when mode request, switch state or status frames from this module look invalid. No manufacturer documents U0439 publicly. Ford and Land Rover both call such a unit ATCM: Ford's SSM 54656 for 2025-26 F-150 finds a 4L switch held down by trim, logged in the ATCM, and Land Rover's SSM73849 covers ATCM variants the Pathfinder tester could not recognise, which shows the module also handles off-road switch inputs. If terrain data is invalid, receivers will typically fall back to the normal road setting, so off-road modes or low range may be unavailable. U0138 is lost contact.
- What you may notice
- Check 4x4 or terrain system message
- Drive mode selection does not respond
- Likely causes
- PossibleTerrain or 4WD mode switch stuck or obstructed by trim
- PossibleAll terrain module software or variant coding wrong
- RarePoor supply, ground or connector at the module
- Repair
- Medium · Usually a job for a workshop.Typical cost: €40 – €800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.