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I bought a Certified Pre-Owned 2010 Sierra SLE 5.3L (LC9) Vin code "3" about 3 years ago. It's stock besides a front leveling spacer on the strut, no aftermarket electrical. The truck will intermittently go into limp mode with "Service Stabilitrak & Service Traction Control" displayed on the DIC (No SES Light). Eventually when the CAN bus reboots the SES light illuminates. After clearing the codes it drives normal until it happens again. I've had it happen on the freeway, in park, on normal surface roads, over bumps, doesn't seem to be a reason why or when it occurs other than outside temps. The odd thing is it only acts up when its warmer than 60 Degrees outside, this winter she drove fine without a single hiccup. Which tells me it might be an internal module failure... However, I've had it happen in the same spot on the way to work several times. When I pull the DTC's it's from modules that lost communication on the high speed CAN/LAN buss or modules requesting MIL because of no ability to communicate. DTC's: U0073 - Communication Bus A OFF U0100 - Lost Comm with ECM U0101 - Lost Comm with TCM P0700 - TCM Request MIL P069E - Fuel Pump Control Module Request MIL U0140 - Lost Comm with BCM U0121 - Lost Comm with EBCM U0102 - Lost Comm with Transfer Case Cntrl Module - I've replaced the battery (Optima Red Top), cleaned the terminals and cleaned Mega Fuse. Tested Alternator with a Midtronics GR8 - Cleaned the Grounds on the Front Engine Block, Fire Wall, Chassis under drivers door, front frame by radiator. (Hood to Firewall ground strap missing) - Removed the UBEC fuse block and swapped relays, no corrosion, applied dielectric grease. - Removed the TPA lock on the TCM/ Trans connector, checked for backed out terminals or ATF leaking. Found nothing abnormal. - Checked the Harness from the TCM going up to the Engine Block, nothing abnormal. - Checked EBCM connectors & harness, nothing abnormal - Checked FPCM connectors & harness, nothing abnormal - Replaced 120 Ohm Terminating Resistor (Twice) - Checked ECM connectors & harness, nothing abnormal - Checked BCM Connectors, nothing abnormal - Checked harness on top of engine, nothing - Using a DLC Break-out box, I have 60 ohms on PIN 14 (CAN High), but haven't been able to test when it acts up. - I can talk to most modules with my scan tool when the CAN bus is online, if I plug it in just after the bus went down, I cant communicate and have to wait until the bus reboots to clear the codes and get back on the road. I used to be able to clear the codes "on the fly" while driving but it seems like its taking the bus longer to reboot as time goes on. Just ordered new Positive and Negative battery cables, and the Hood ground (not sure why the hood needs a ground) Could the VCIM module be bad? The truck is pretty much babied since I've had it, I change the oil myself every 2-3k (fear of AFM issues). Any help is much appreciated. I'm running out of ideas.