MontanaSteve

After over 40 days without my truck, it's supposedly fixed and ready for pickup. They replaced several wire harnesses. The one that fixed it was from TCM to ECM. Supposedly. In the meantime, I found a near-mint, but high-mileage, bone-stock, never-tuned/modified, 2004 Ram 2500 5.9L Cummins with the 6-speed. Owned by two different old guys that know each other, never towed anything heavier than a drift boat (has never had a hitch mounted in the bed, so I believe that's probably true). I'm selling the Chevy if it's actually fixed. I've lost confidence. I will miss that heated steering wheel though - that was real nice in Montana.

Got my truck back from the dealer last night, with a new TCM. Made it about 20 miles before the truck violently shifted again, with all the same messages. I just tightened my fuse box bolts, which is annoying as **** since I took the time to email the service rep the TSB about it. It took me longer to find my in-lbs torque wrench than to tighten the bolts. I got from 1/4 turn to 3/4 turn on my bolts. Crazy that a tiny adjustment like that could cause such an issue, but here's to hoping.

Thanks Jay. I had seen that already posted by you and passed that TSB on to the service rep. She ignored it, as there’s nothing in the service write up about it. They put a new TCM in, gave it back to me, and it happened again 20 miles after leaving the dealer. I’m checking the fuse box bolts tomorrow myself.

Following. Somewhat similar symptoms, though mine occur after a random shift in the transmission. Has happened three times. First was slowing to a stop sign, maybe 10mph. The truck jolted hard, I thought I had been rear-ended, but nobody was behind me. Got the service parking brake, service ESC, traction control off, and CEL. Second time was leaving a stoplight, when it jolted hard, upshifted several gears and stuck there, same series of warning lights. Third time, driving home doing 70 mph, jolted again, felt like I had hit an elk, same warning lights, and I was now in a much lower gear and stuck there. I tried shifting to manual mode, but no gear indicator showed, and the +/- buttons did nothing. All three times required me to pull over and restart the truck. Dealer has had it for a week. They put a new TCM in the truck, but couldn't get it programmed correctly. They're now looking into wiring troubleshooting. One guy on the 3.0 Facebook page had the same symptoms. His dealer found heat damage to the wire harness where it was routed against the exhaust downpipe. I told my dealer that, but they're following the GM troubleshooting steps first. So now I'm in a loaner Colorado that I'm not allowed to take offroad, or use for towing - during hunting season. And I need to get firewood.

My buddy’s 2020 is having the identical symptoms to yours. I’m having a somewhat similar issue in my 2020. Both are currently in with the local dealer. Mine was more transmission-related symptoms - jolting and slamming into a gear while moving. Happened three times, accompanied by “Service Parking Brake,” “Service ESC,” and “Traction Control Off.” It’d be stuck in that gear until restarted. I’m betting my buddy’s rig has the same loose fuse box bolts as yours. Mine could possibly be related. Gonna check this bolts when I get it back, if the dealer doesn’t do it. Thanks for the response. Cheers.

Forest, did this resolve your problem? Thanks.