Originally Posted by
Eddie-98GTP
Has anyone tried to tap into the network without taking the PCM offboard? For example, looking at my network diagram (2021 Colorado Diesel), the GMLAN bus runs from one module with a terminating resistor, through all the other modules on the bus, to another terminating resistor (I know you already know this). The PCM has one 120 ohm resistor, then the network goes through the transmission module, then the transfer case module, then... the ... front view camera. If I were to disconnect the camera, and use terminals 5 & 6 (the GMLAN bus) to connect the HPT interface to the network, this would effectively isolate the PCM, TCM, and Transfer case module from the rest of THAT network, possibly getting around the security issue. Any ideas? I have to take my truck to the dealer tomorrow morning to have the transmission replaced so I'll be unable to test this. Has anyone tried anything like this? If it works, the PCM and TCM could both be read without having to remove them and make a complicated jumper offboard harness - the camera is pretty easy to get to. I just don't know enough about the network protocol to know if this is even an option.