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U0285 Lost Communication With Active Grille Air Shutter Module B

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Corrosion in the lower shutter harness or connector from water and salt
Lower shutter or its wiring damaged by impact or debris
Shutter actuator B internally faulty

Symptoms

  • Malfunction indicator lamp on, often with P05AE
  • Lower grille shutters do not move
  • Active air flap warning message

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–700
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

active grille shutter module bvehicle bus wiring

Related codes

U0284U0586P05AEP05B1U028B

References: gsi.ext.gm.com, fordservicecontent.com, static.nhtsa.gov, static.nhtsa.gov.