Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
I have a 2007 Chevy Equinox AWD 3.4L V6. I am having transmission issues and need to reset the TCM to relearn the shift patterns. The issue I have is I cannot talk with the TCM using my Tech2. I can talk with every other node on the CAN but not the TCM. I have checked the CAN voltages they are within spec 2.3V and 2.7V. Resistance tests show no grounds or shorts that I can see 60 ohms on the dot, with TCM removed 120 ohms measured to the end resistor and 121.8 back to the ECM. I replaced the TCM and had it programmed for my VIN and still no communication. I replaced the ECM and programmed it myself no issues there and still no TCM communication. I tried and reprogrammed the TCM and it communicated fine through SPS but then no Tech2 comms. I checked the voltage from the battery at the TCM connection and reading 12.2 volts = battery voltage. The ACC signal from BCM reads a bit low at 11.7 volts but there. I'm really lost on what to do next. Any help? Can I some how wire up a bench CAN loop?
Maybe try a different scan tool to see if it can communicate with the TCM.
Another thought is check the VIN is entered correctly in the Tech 2. If the tool thinks the vehicle is a stick shift it won't be trying to communicate with the TCM.
This is my CAN bus on the scope. The top lines are my scopes explanation of what it should look like. The bottom lines are my CAN buss. I get this with the old ECM and it’s the same with the new ECM.
That wave form does not look good. I would say to do a pin drag test on the connectors and inspect pins for corrosion/ fluid intrusion and check /clean ground points for tcm, fuse box and pcm. But with the communication working on sps i would say you china knockoff is the problem. However one way to tell is to unplug on module at a time on that section of the network and see if signal improves and comms work again with tech 2. Other wise find a identical car and test comms with it.
As for the adapt relearn can you clear shift adapts with the sps? If so the relearn procedure is done without a scan tool it has 25 steps and repeating parts of it 5 to ten times.
tested the can bus on my 2014 Ram and it looked the same on the scope as my equinox did. so i have an issue with my scope. I just bought it. Its a Hantek 1008c. I'm a little disappointed with it. I really don't see a way to calibrate it. So my Can bus must be fine. I really at lost on why I can't communicate with the TCM. I have checked all of the connections voltages and grounds haven't found anything unusual. Resistance is 121 ohms. End resistors are 60 and 61 ohms.
Topic Author
