U0285Lost Communication With Active Grille Air Shutter Module B
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Module B is the second shutter unit, typically the one behind the lower bumper opening. GM's 2018 ECM tables treat it as LIN device 1 (shutter 2): the ECM sets U0285 after 3 missed counts once the check has been enabled for 400 ms in Run at 11 V or more, Type B with MIL after two trips. Ford monitors it together with A in its OBD summary (signal missing over 10 s). Being low at the front, B collects water and road salt: Stellantis case S2523000095 for the 2025–2026 Ram 1500 reports a lit MIL with U0285 and P05AE and checks the lower shutter harness for corrosion first, and Hyundai's campaign 26-01-026H for the 2026 Palisade replaces corroded lower flap wiring, actuators or sensors. The lower shutters then stay put.
- What you may notice
- Malfunction indicator lamp on, often with P05AE
- Lower grille shutters do not move
- Active air flap warning message
- Likely causes
- LikelyCorrosion in the lower shutter harness or connector from water and salt
- PossibleLower shutter or its wiring damaged by impact or debris
- RareShutter actuator B internally faulty
- 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: €30 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.