CAN network

U0284 — Lost Communication with Active Grille Air Shutter Module

Severity: medium Safe to drive

What U0284 means

U0284 means a control module stopped getting responses from the active grille air shutter module over the CAN bus. The shutters normally close to improve aerodynamics and warm-up, and open to let air through for cooling. Without communication, the system cannot command them or know their position.

Symptoms

  • Check Engine or other warning lights on
  • Cooling fan runs more often or louder than normal
  • Reduced fuel economy
  • Slow engine warm-up or overheating in heat
  • Shutters not moving, or clicking sounds from the grille area

Possible causes

  1. Failed shutter actuator motor
  2. Debris, ice or an object jamming the shutters
  3. Damaged CAN wiring near the front bumper
  4. Open, shorted or chafed CAN bus harness
  5. Corroded connector terminals at the module
  6. Power or ground fault at the shutter module
  7. Another faulty module loading the bus

How to diagnose

  1. Scan all modules and map which ones are not communicating
  2. Inspect the shutters from the front for damage, debris or binding, and make sure they move freely
  3. Check the module connector and harness for corrosion, damage or impact marks
  4. Test power and ground at the module connector
  5. Measure CAN bus resistance and voltage at the diagnostic connector
  6. Check continuity of the CAN-H and CAN-L wires to the module
  7. Run the shutter actuator test with a scan tool if supported
  8. Disconnect modules one at a time only per a documented procedure

Common fixes

  • Clean the shutters and clear any jam
  • Replace the shutter actuator or module
  • Repair the front harness or connector on the CAN circuit
  • Restore power and ground to the module
  • Replace a faulty module that is loading the bus, then clear codes

U0284 on different brands

Ford · manuals
Ford lists U0284:00 as loss of communication with active grille air shutter module "A"; it identifies the monitor condition, not a confirmed failed part.

Questions and answers

Can I drive with U0284?

Usually yes, but carefully. If the shutters are stuck closed, overheating is possible, so watch the temperature gauge and diagnose it soon.

What most often causes U0284?

Most often a failed shutter actuator, a damaged connector or wiring in the front bumper, or jammed shutters. Start with a visual check and power and ground tests.

Does U0284 affect fuel economy?

It can. The shutters help aerodynamics and warm-up, so a failure may raise fuel consumption slightly.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.