Hey guys new here, just purchased a downed 2012 Chevy 3500. I have no comms to any of the major control modules. I did an Ohm test on DLC Pins 6 and 14 I only have 1.5 Ohms I was told it should have 60 Ohms. I have replaced the ECU and Tested the terminating resistor on the high speed Can bus which is 120 Ohms which is correct. Any help diagnosing would be appreciated.

 

Check all of your fuses for continuity . Especially the ones in the underhood fuse panel .
There are TWO 120 ohm terminating resistors on the network , One at each end .Their combined functional reading = 60 Ohms on the CAN Data Buss .
You are checking the fuses specifically for corrosion that causes the fuse to appear good but fails continuity test (Removed) due to being corroded in half at the base .
CAN data buss requires Power in order to operate . I lived this same nightmare for a week one day on my ‘07 Silverado .
Do yourself a favor and take the time to test each and every fuse ( removed ) and inspect for corrosion . apply a NON-Hardening anti-corrosive compound to the fuses and the sockets they plug into . Vaseline is inexpensive and works well and can be applied with a Q-tip .
I used “Truklite NYK-77 “ anti corrosive compound .
I have had no repeat issues since replacing the 6 corroded fuses and servicing the fuse sockets and relay stabs and sockets .

Good luck .
If the fuses and relays service does not help and you cannot find the second resistor . someone may have cut it out of the CAN .
CAN = Controlled Area Network.

 

So a little more insight on the truck it sat in a lot for about 6months and some bums where caught trying to steal it but no wires were cut that I can find.

 

I’ll stand by my original recommendations of checking all fuses and relay stabs as well as application of some form of Non-hardening corrosion preventative . and then searching for the second termination resistor .
Are there any other lights or fault codes present ?
You should have a bunch that begin with the letter “U” if you have no active comms .

 

This is what i mean by no comms, they arent even showing up.

 

As far as I can see 3 modules Passed and your HVAC ( H eating V entilation A ir C onditioning ) Shows 2 Faults .
And given the age of the truck they are most likely Air damper motor faults (Most common) among HVAC issues .
I am not familiar with the Autel tool and how it maps out fault codes .
If you expand the codes by tapping the blue arrow does the tool display any additional data ?
What you need are specific fault codes
What you are showing us is similar to a general systems “Health Scan” on my Launch X431 tool .

Also if your other modules are actually not communicating the first place to look is always “ Power or the Lack of Power to those modules”

In my particular past i had Body control module issues and Supplemental Restraints issues .
After i found all the bad fuses and cleaned all the corroded fuse and relay terminals the modules resumed proper function after power to them was restored .