Bought the truck a year ago, knowing it was throwing this P2135 code. When it happens it says "reduced engine power, service traction control, service stabilitrack", and I have a scanner hanging from the turn signal and sometimes I can just clear it while driving, sometimes have to stop and turn truck off, open door, close door, key on, clear, then its fine for another week or 2.

Previous owner replaced:
Throttle body with O'reillys aftermarket
Alternator
Fuel pump
Swapped a known good PCM with no change

I replaced:
Throttle body with used GM TB
Throttle body sensor with new in box/bag GM sensor
TB pigtail with Delco
Evap solenoid with delco (got a code for this)
right front wheel speed sensor with delco (got a code for this)
Cleaned throttle petal connector but its date coded 2014 have not replaced this yet.
Disconnected, sanded, cleaned, reattached all grounds I could find including back of driver cylinder head. Also ran a temp ground from here to no avail.
Pulled fuse box and cleaned all connectors, underside of fuse box, pulled and cleaned any fuses related to PCM or network or anything, reinstalled with dielectric grease. This was prompted when it started throwing "trans module cant see fuel pump cant see network yada yada" codes and was shifting like ****. That issue has been gone since I cleaned the fuse box.

Still getting the P2135 code, but also now getting a cylinder 4 misfire code that also triggers service traction control. That only happened after I had disconnected the battery to clean the fuse box, thought it was a slightly clogged injector that when it lost its long term fuel trim that it acted up, because if I clear the code and drive for a bit it goes away. Did purchase a fuel injector cleaner tool and will do that today when it cools down.

What is next? Anyone else fight one of these issues before? My next guess is replace the throttle petal, the entire fuse box, or replace the PCM. Not sure if the cylinder 4 code is related or Im fighting 2 issues.

Havnt been on here in a long time but the camaro still lives, you can see it in the street. It normally lives in an enclosed trailer for the past 5 years waiting for me to stop having kids.

 

A SWAG.....
"service stabilitrack",
Different diameter tires ft to rear?

 

They are all 35x12.5 R20s, but they are different brand front to rear, but both measure very close in size.

The very very odd thing; sometimes it throws the code when its not even running. Like Ill drive to the store, come out, hit the key and get nothing, but see the codes on the dash, clear the codes, then its fine. Or one time I was sitting in the driveway watching live readings on my scanner, just scrolling through the pages with the key on, and it did it. I was watching the throttle petal and the throttle body responses on the screen, and did see the blip in the throttle body position when it did it once, so something is grounding/shorting/loose somewhere on that 5v circuit that is shared by a lot of the different systems on the truck.

 

Update on this for anyone who runs into this issue. I found a video on youtube about how theres 2 120 ohm resistors in that canbus circuit, and if you put your meter across pins 6 and 14 on the OBD II port, you should get 60 ohms because the resistors are in series if both are there. I got 120, which means there was a break somewhere in the circuit. Ive always had random slip lights on the dash around sweeping corners for traction control, and the "service stabilitrack, service traction control" messages when it does P2135, and so started with the ABS block connector. Pulled that off, didnt see much, left it dangling but then went for a test ride and all the codes were gone except "cant see the abs module" for obvious reason. The dash looks like a christmas tree with every light lit up, but knock on wood no issues since. Im going to give it a week or 2 to see if any of the comms codes come back, or if P2135 happens, but fingers crossed it was just a bad connection at hte ABS module, or at worst, just replace the abs module. Will update again in a few weeks.

 

Update: P2135 showed back up today. So thats unrelated to the comm issues I guess.

 

Why does the first photo of Avalanche appear to show extreme tire diameter mismatch ?

 

You've got an issue with the TPS/pedal position voltage mismatch

 

that code is for your throttle position sensor bud.. need to replace it... do a google search for: GM DTC P2135