Replaced active shutters and still getting CEL. What's next?

Josh Chew · August 6, 2023

Good day,

2020 Sierra 1500 Denali

Getting the following CEL codes:
U0284 - Communication with Active Grille Air Shutter 1 Motor Module
U1345 - Engine Control Module LIN Bus 1

I replaced the active shutter assembly (seemed to be the most common fix), removed the negative battery terminal for 15 minutes to reset the CEL, and after about 5 minutes of driving the CEL came back on. The codes remained the same. What's next to diagnose this problem? I couldn't care less about the active shutters, but the CEL prevents me from remote starting the vehicle.

My skills are limited to replacing parts, which I'm comfortable with anything up to the engine/transmission. Could someone tell me how to diagnose using a multimeter and what wires I need to check and what settings? Or is it at the point that I need to take it to a mechanic?

Any help you can provide is greatly appreciated

David Krueger · August 6, 2023

I had a problem once with replacing parts, and the computer didn't read them or pick them up. The fix was to find the fuse that controlls the part and remove it for a bit. Same thing that disconect the battery does only the computer is still active. Turned the switch on and off, then put the fuse back in and start the vehicle. the computer found the new part and light went off. I don't know if this will work but it's worth a try. You will have to look in your manual to find the correct fuse.

Transient · August 7, 2023

I think David Krueger is on the correct path. Go up-wire from the plug into the active shutter motor. Look for damage to the wires. Check the fuse in the fuse box, etc.

repairman54 · August 7, 2023

Doing your own wrenching, get the shop manual for your truck. alldatadiy.com has the complete one with diagnostics, wiring diagrams and how to disassemble things online. 3 yr subscription is less than 1 hour of shop time.

I have one for all the vehicles in my fleet.

johnwall · January 5, 2024

Josh Chew did you ever get it fixed? If so what was the problem? I have the same codes. Thanks

Josh Chew · January 5, 2024

Sorry for not following up. I ended up taking it to the dealership and it was a wire that rubbed through the outer sheathing. Highly recommend tracing the wires before ordering and replacing the active shutters. It would saved me $600 for the part and a morning of my time.