yellowGT

So...i have a harness from a 2012 escalade 6.2 and I figured out that the wires for the obd are pins 27 and 28. I followed the wires and they go to what I think is the trans plug. Now, is the tcm inside of the 6l80 and do I clip before or after the trans plug to take wires to obd plug?

1989GTA

The wiring goes from the ecm to the tcm in the 6L80. Then it comes out of the tcm and it can go to the OBD plug. Anyways that is what I did and it works just fine.

brandon6.0

iTrader: (32)

yes the tcm is in the 6l80e. I just built a harness like this yesterday. Pull the canbus wires from the plug that used to go to the cab. The new stuff is all canbus and doesn't use a serial 2 wire like the older stuff. It should be Canbus - and Canbus +.

http://r.search.yahoo.com/_ylt=AwrB8...c6.8MKb3D4oHA-

1989GTA

One more thing. I installed I believe a 120 ohm resister across the Canbus wires at the OBD plug to signal the end on the communication chain. I used like an 1/8 watt resistor.

brandon6.0

iTrader: (32)

Ive never had to use a resistor or anything like that. I just wire them up to the obd2 port as the diagram I posted and all is good to go. Hptuners was reading correctly and had no problems adding a tune to the harness I just built the same way.

yellowGT

yes but what I'm asking is if the tcm is inside the transmission somewhere because the tan and tan/blk wires that are twisted go to the transmission plug then come back out so I don't know where to cut them in order to take them to the obd hook up

EFIHARNESS

You can cut them after the trans connector. So they go from the ecu ,to trans, then to obd 2. The ecu needs to talk to the trans. We have not needed the terminating resistor. We have made several hundred of these systems set up like this. Steve

pdxmotorhead

Need is relative, its not required but its a good idea to terminate the can bus, it keeps transient signals off the bus, and helps it run cleaner. Not a earth shattering problem, but if you have a bad electrical issue(Someone welds on it without proper strategy) it helps protect the ecu and the integrity of the control signals. If your running any external high grade diagnostic gear on the bus it will let you get full speed transfer of data. I've had to work on some equipment with CAN that definitely ran happier/faster in data acquisition mode with the proper terminations..

yellowGT

Thank you guys!