P2C78: Active Grille Air Shutter Module D Over Temperature

What it means

The control module of active grille air shutter D reports junction temperature above its protection threshold. Thermal protection has triggered.

At a glance

• Usually lights the check-engine light

How it works

The active grille shutter D module drives and monitors the actuator for shutter D, one of the vehicle's movable grille panels. This code sets when the module reports its internal junction temperature above its protection threshold. The module may limit shutter operation to protect itself.

Common causes

Most likely first.

1. Under-bonnet temperature too high
2. Sustained stall current

Symptoms

• Check-engine light
• Active grille shutter warning, if equipped
• Grille shutter operation may be limited

How to diagnose it

1. Read freeze-frame data and module temperature information, if available, to determine whether the overtemperature occurred during unusually hot conditions or repeated shutter operation.
2. Inspect shutter D and its linkage for a jam or obstruction that could make the actuator draw current continuously.
3. Check the actuator connector and wiring for damage, poor contact, or signs of overheating.
4. After the assembly cools, command shutter D with a scan tool and watch for binding, repeated retries, or a return of the temperature fault.
5. Test the D actuator and module supply circuit for abnormal current or resistance according to the manufacturer's specification.

Common fixes

• Remove debris or ice that is making shutter D stall.
• Repair a damaged connector or wire causing poor contact or excess load.
• Replace the shutter D actuator if it stalls or draws excessive current.
• Replace the D control module if circuit and actuator tests pass but its temperature fault recurs.

Can I keep driving?

A short trip may be possible if there are no temperature warnings and the grille is unobstructed, but shutter operation may be limited. Watch the engine temperature and stop if it rises above normal.