P2C78: Active Grille Air Shutter Module D Over Temperature
The control module of active grille air shutter D reports junction temperature above its protection threshold. Thermal protection has triggered.
What P2C78 means
P2C78 is a generic OBD-II powertrain code in the cooling group.
- Check engine light
- Usually on
- Emissions-related
- No
- Limp mode possible
- Not typical
- Drive cycle to clear
- Not required
Get it fixed
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Common causes
- 01Under-bonnet temperature too highMost likely
- 02Sustained stall currentPossible
Can I drive with P2C78?
No. Stop and let the engine cool.
If the temperature gauge is high or you see steam, pull over and switch off. Driving an overheating engine can warp the head and blow the head gasket.
Why we rate it urgent
- Engine over-temperature can cause head-gasket and engine damage
- Turns on the check engine light
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose P2C78
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just P2C78. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Check for related codes first
Look for P2C75, P05C1, P05C0. Related codes often share a cause; a circuit or sensor code usually needs fixing before a performance code like this one.
- 3
Check live data
Watch the related sensor and actuator readings in live data (Active grille shutter D, Wiring harness, ECM) and compare them with expected values in the service information for your vehicle.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Under-bonnet temperature too high; sustained stall current. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and drive the car under the conditions in the freeze-frame data to confirm it does not return.
P2C78 repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Moderate
- Good DIY job?
- Usually a shop job
Needs a scan tool and some experience with testing.
Parts and systems involved
- Active grille shutter D
- Wiring harness
- ECM
P2C78 FAQ
What does P2C78 mean?
P2C78 means “Active Grille Air Shutter Module D Over Temperature”. The control module of active grille air shutter D reports junction temperature above its protection threshold. Thermal protection has triggered.
Is P2C78 serious? Can I keep driving?
We rate P2C78 as urgent severity. No. Stop and let the engine cool. If the temperature gauge is high or you see steam, pull over and switch off. Driving an overheating engine can warp the head and blow the head gasket.
What causes P2C78?
The most common causes, from most to least likely: Under-bonnet temperature too high; Sustained stall current. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix P2C78?
Typical labor is about $65–$375 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix P2C78 myself?
DIY difficulty is moderate. Most owners leave this to a shop because it needs involved testing or specialist tools. Always confirm the cause before buying parts.
Will P2C78 clear itself?
If the fault was intermittent, the warning may go off once the computer stops seeing it, but the code stays in memory. Fix the cause; clearing the code alone doesn’t repair anything.