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2021 GMC Sierra SLT diesel with check engine light on

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My truck check engine light came on at 3200 miles.  Took it to McKenzie GMC in Milton FL.  Codes were pulled U0285 and U1345.  So they replaced a grill air shutter motor module.   Was told to come pick it up all fixed.  Get there and check engine light still on!!!  Thoroughly disgusted.  Now having to wait on more diagnostics!  Any advice?



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Engine Control Module LIN Bus 1 (or Bus 21)



Lost Communication with Active Grille Air Shutter 2 Motor Module


The U0285 explains why they went after the shutter, but I wonder if they ignored the two bulletins in relation to those codes that are a possibility.


#PIT5689D: No Restart after an Auto Stop Event / No Crank / Dead Battery / DTC P0562 P0617 P0621 P0622 P0700 P1005 P26E6 P305D P305E P2796 U010E U0102 U0106 U0284 U0285 U0672 U029D U029E U02A1 U02A3 U0623 U111A U111E U1348 U18DE - (Jun 10, 2021)




#21-NA-149: Engine Wire Harness Chafing - (Jan 5, 2022)


The first one is an inspection of two ground straps on the passenger side of the wheel well area.  The second one is the potential areas for wire rub-through.


I'd mention those two bulletins to them, see if they pursue.  You southern states I wouldn't expect a lot of shutter replacement since you guys don't get snow and salt shoved up in the grille.  We do shutters up here in NY a good bit on K2 trucks (2014-2018) for U1510 code and a check engine light.  

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  • 2 years later...

Was this problem solved? I have a 2020 Chevy with a Duramax currently at 128k miles. I recently put wide tires and and after the tires beating up my fenders for clearance I have the U1345 code. I’m sure it’s something dumb from the tires but I was curious to see what your fix was. 

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