U0285
Lost Communication With Active Grille Air Shutter Module B
The vehicle bus reports loss of communication with active grille shutter module B. The aerodynamic flaps in front of the radiator stay in their default position, increasing drag and possibly affecting cooling.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Common causes
Ordered by how often each turns out to be the cause.
- Bus wiring open or shortedCommon
- Module without power or groundPossible
- Module failedPossible
Parts involved
- Active Grille Shutter Module B
- Vehicle Bus Wiring
U0285 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.