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Sharing experience for your info and any ideas you might have. My shiny new 2021 GMC Sierra Denali 3.0 Duramax Diesel with 4900 miles on it has been losing its mind. I get multiple, rotating DIC messages: “Service ESC”, “Service Parking Brake”, “Service ABS”, “Adaptive Cruise Control Disabled”, “Steering Assist Reduced Drive with Care”, . . . ). The error messages come with other “benefits” besides disabled cruise control. I also enjoy no GPS signal, no Blind Spot sensors, no collision avoidance sensors, and who knows what else. Fortunately, the diagnostic codes were stored so the tech could see them, and I provided video of the DIC messages each time, too. They are on their 4th attempt to repair it now. First time, they replaced the Exhaust Particulate Matter Sensor (4025920) . Second time, they tried the same thing and replaced the Exhaust Particulate Matter Sensor, again. The 3rd time, they inspected the engine harness but found no damage so they replaced the pigtail to the Exhaust Particulate Matter Sensor and followed an 8 hr rest cycle and road test protocol. It worked for about 2 hours after I picked it up, then everything lit up again. This (4th) time, they are saying they will replace the entire wiring harness per GM’s direction. I do not want to use Florida’s Lemon Law, but I am starting the process just to be safe. BTW, I’m also getting the “long-crank/no-start” issue. They just applied the ECM update per TSB for this problem, so we’ll see if that worked when/if I get to keep the truck more than a couple hours between service appointments. I was having issues with the passive locking feature where the truck locks the doors a few seconds after I get out with the key in my pocket. It would not work even when set to on. Now that they did the Infotainment software update (V155) this seems to be fixed. I’m still having false messages that the SD Card for the Navigation System has been removed when it has not been. GM has a bulletin out so they know about this issue, but it appears there is no fix action on this one yet. After looking up each code listed on the repair orders (RO’s), I believe the main harness is a very likely cause of all the DIC error messages and system failures. Otherwise, all those modules and sensors involved have gone bad simultaneously. I suppose a power surge of some kind could do that, but then it seems the modules would not work fine in the short time between repairs. Here are the codes the tech reported on the last two Repair Orders (bold codes where noted on both RO’s): 2/5/22: B1A01 Speaker 1 General Electric Failure B395B Side View Camera Left P1488 Particulate Matter Sensor Protection Tube Performance U0020 Low Speed CAN Bus U0022 Low Speed CAN Communication Bus (+) Low U0077 Control Module Communication Chassis Expansion CAN Bus U0121 Lost Communication with Electronic Brake Control Module U0151 Lost Communication with Inflatable Restraint Sensing and Diagnostic Module U0155 Lost Communication with Instrument Panel Cluster Control Module U0184 Lost Communication with Radio Unit U0415 Invalid Data Received From Electronic Brake Control Module U0422 Invalid Data Received From Anti-Lock Brake System Control Module 2/10/22: B0967 Parking Aid On/Off Switch Circuit Short to Ground B1AO1 Speaker 1 General Electric Failure P1488 Particulate Matter Sensor Protection Tube Performance U0077 Control Module Communication Chassis Expansion CAN Bus U0121 Lost Communication with Electronic Brake Control Module U0131 Lost Communication with Power Steering Control Module U0151 Lost Communication with Inflatable Restraint Sensing and Diagnostic Module U0184 Lost Communication with Radio Unit U0415 Invalid Data Received From Electronic Brake Control Module U0421 Invalid Data Received From Suspension Control Module U0422 Invalid Data Received From Anti-Lock Brake System Control Module