Originally Posted by Mclaughlincole

Anyone have any input on this? I have a 13 2500hd ltz and does the exact same stuff, have replaced battery cables with larger ones that I built, cleaned all grounds, replaced resistor, etc, the only thing that I have done different is i unplug the abs control module everything nothing goes back to normal caster except for the obvious stabilitrac, abs, brake and traction control light comes on, but gauges go back to normal, starts like brand new, bought new replacement and module and tried it and same problems no start, guages going crazy etc, leads me to believe that must have some corrupts or problem with the can/bus line, very familiar with this type of system (class 8 truck mechanic) over the road semis are using it for everything these days, just not sure where to start looking on passenger vehicles

Originally Posted by tech2

post the communication codes that are setting and the modules the codes are set in. u codes or undefined codes will require a full function scan tool. the can bus network is wired in a daisy chain configuration...unplugging the module separates the bad part the circuit so the network starts communication again. the problem is downline of the abs module or the abs module.

Originally Posted by Mclaughlincole

So today did a little trouble shooting, after following the harness along the frame looks as if the itbc module is the last in line, so unplugged and problems went away, kinda had a hunch that maybe something has been wrong with it since I have owned the truck for last 8 months, when I hook up a trailer I don't get any "trailer connected" message, nor can I bring up output gain in the DIC, but if I use manual slide it will sometimes feel like brakes on trailer work, trailer is brand new and works just fine in my older truck and motorhome, got new module ordered today, will update if it fixes it

Originally Posted by tech2

to verify the wiring is good before replacing a module...do a terminating resistance check and CAN+ and CAN- voltage checks. these will tell you if the bus is open, shorted to grd, shorted to voltage or shorted to each other

Originally Posted by tech2

the termination resistance should be near 60 ohms so you are ok. each end of the bus has a 120ohm resistor if one bus wire was open you would get 120ohms. wires in parallel should read 60 ohms. this test should be done with the battery disconnected. after you can check for short to grd on each line...should be OL
to check the can high and low wire voltages:
connect the battery
from the dlc connector measure from grd….. high side should be approx. 2.5 and low side should be 1.5v while the bus is awake...iirc

Originally Posted by ctandc

I used to be a GM tech. I've been wrenching on cars / trucks for more than 25 years. Owned plenty of GM products, but I think this might be my last one.

In August '16 purchased a used 2011 Silverado 1500 4.8 2WD for my college aged son's primary vehicle. 60K miles. Very clean truck. Even though it was a 2WD a previous owner had installed a reputable aftermarket "leveling kit". This only consists of a metal spacer under the strut and and blocks in the rear lead springs. Larger tires / aftermarket wheels were installed. When I bought the truck, the TPMS light was constantly on and it appeared to be getting no signal from the TPMS system. Since I planned on installing new tires, I went ahead and ordered new AC Delco TPMS sensors for each wheel and had them installed when the new tires were put on. Turns out there were no TPMS sensors AT ALL before, as I suspected. I then programmed the TPMS system via the remote entry FOB and TPMS worked perfectly. No check engine lights.

Truck was driven daily for several weeks before the new tires and TPMS sensors were installed. A little while after tire / TPMS install my son reported the truck "acting weird". I scanned it, no outstanding codes and didn't think about it. A few days later it happened again and I witnessed it. While driving on the interstate, the Stabilatrak light lit up, then the DIC reported it was disabled and then reported Traction Control was disabled. When this happened, the speedometer dropped from 60mph to 0 mph and then bounced back and forth several times. Truck would stop doing it on it's own. When this happened, if traveling at low speeds, the transmission would shift extremely late and abrupt. Pulled the following codes from the truck:

P069E
P0700 - Transmission control system
U0073 - Control Module Communication Bus OFF
U0101 Lost Communication with TCM
U0109 Lost Communication with Fuel Pump control
U0100 Lost communication with ECM/PCM 'A'

Searched on Google, found a reference to a TSB and possible bad negative battery cable. Pressed for time (Son was going off to college - taking the truck - ironic it was bought so he'd have a reliable vehicle I didn't have to work on all the time) I installed a new GM Negative battery cable, cleaning all ground connections and making sure everything was connected good. Went ahead and replaced the battery since it was the original and 6 years old by the date code.

Son left for college. Problem still occurred and seem to occur more often. Searched some more and had the truck taken to a Chevrolet Dealer I've dealt with before and explained all the issues. They had the truck a full day and of course could not reproduce the problems. Recorded video of when it happened, showed them, they took it again and supposedly checked EVERYTHING listed on the GM TSB regarding electrical issues with these vehicles. They found that the wiring harness plug entering the EBCM (Electronic Brake Control Module - on the frame rail driver's side - the actual connector on the computer, one of the tabs that lock the harness in place was broken. They cable wrapped the connector, drove it several miles (at my request) and it seemed to be fine.

I bought a replacement, brand new GM ECBM ($180 my cost versus much higher through dealer) just in case. Issue started occurring again, and then a day or so later my son called me - the truck seemed completely dead (had power to all accessories) but would not even attempt to start. I drove to where the truck is to look at it. Battery was fine. I removed the cover from the underhood fuse box to check fuses / relays. Pulled the main start relay and was greeted with GREEN corrosion on the prongs on the relay. Pulled every relay / fuse, cleaned all contacts with sign of corrosion, used a bit of dielectric grease, truck started right up - drove with no errors.

Two days later, SAME symptom. No start. Took back to same dealer and showed them the corrosion on the fuse box. They replaced the entire fuse box (Comes with new relays).

So now I'm around $700 into this thing (out of warranty of course).

Symptoms came back a few days later. Son had to actually pull a main relay from the fuse box, reseat it and truck would start. Error lights and gauge cut out would happen randomly. Including lovely hard shifts (TCM not communicating).

I added a larger engine to chassis ground, ensuring all connections were solid. I also installed the ECBM I'd bought earlier. The existing part actually seemed to have burnt looking connections inside of it. Of course had to have the new ECBM programmed. The same Chevy dealer (today) had trouble getting it programmed. Had to talk to GM Tech Support / Engineering and were finally able to get it programmed. On the road leaving the dealership to go back to college, son called to let me know it was doing 'it" again. Gauges acting stupid, stabilatrak light etc.

I found a LONG thread here were several people had luck simply replacing the factory positive battery cable crimped on end. I will try that on both positive and negative cables and this weekend. At this point I'm ready to trade it in on something NOT GM.