U028B: Lost Communication With Active Grille Air Shutter Module C

What it means

The vehicle bus reports loss of communication with active grille shutter module C. The aerodynamic flaps in front of the radiator stay in their default position, increasing drag and possibly affecting cooling.

At a glance

• Usually lights the warning light of the system that lost communication

How it works

Active grille shutter module C operates its assigned front grille flaps to manage airflow and aerodynamic drag. The vehicle network expects status messages from module C; this code sets when another controller no longer receives those messages and cannot confirm the module's state.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

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

How to diagnose it

1. Scan all modules for network and low-voltage codes, and review freeze-frame data to see whether module C is the only node affected.
2. Use a scan tool to check whether active grille shutter module C responds and provides shutter status data.
3. Inspect module C's connector and harness for looseness, corrosion, water, impact damage, or chafing.
4. Check module C's power and ground under the manufacturer's specified conditions.
5. With the vehicle powered down as specified, test the network wiring to module C for opens, shorts, or poor connections.
6. If the circuits are sound but module C remains offline, confirm module failure using the manufacturer's procedure.

Common fixes

• Reconnect and secure the module C connector.
• Repair damaged or corroded wiring or network connections at module C.
• Restore the module C power or ground supply.
• Replace module C if its circuits test correctly but communication does not return.

Can I keep driving?

A short, cautious trip may be possible if engine temperature remains normal and no cooling warning is present, but monitor the temperature and avoid heavy loads in hot conditions. Stop if the engine overheats, because module C's grille flaps may not respond as intended.