TOOSLO5

Confirmed through Brendan at LT1 swap that wire 18 is not needed. Still chasing some other harness wires to see if something else might be damaged which is causing the no start issue.

bsharpe

iTrader: (3)

You need to wire the high speed gmlan network correctly. The tan/ tan black wires are very important. They are like a chain and need to be connected together with a 120 ohm resistor at the start and end. The ecm has the resistor built into it. This will be the start of the chain. Then it connects to the tcm and then it goes to the bcm in my car. It then goes to the dlc which is the end of the chain. I ended the chain by connecting the + and - wires with a 120 ohm resistor. It should look like this. ecm(==tcm==bcm==)dlc. The parentheses are the resistors but you only need to add the one at the end. Since your not ido.g a bcm just remove it from the diagram and go from tcm to dlc.

TOOSLO5

Bsharpe, I currently have the tan, tan/black from both the ECM and TCM tied together and run to the DLC. With a known good ECM/TCM I can read and re write both but it will not start which is why I am questioning the harness or something I have done.

Could this be the cluprit for the no start issue? If that is the case I should run the tan from the ECM to the DLC and a tan/black from the TCM to the DLC with a resistor between the other ECM/TCM wires to complete the circuit.

TOOSLO5

This look correct?

bsharpe

iTrader: (3)

No, both wires goes to each unit. Your diagram is a loop. You want it to be a chain like below.

Ecm====TCM====DLC(with 120 ohm resistor connecting the pins at the back of the connector)

If you are able to read and write to both the ECM and TCM then you GMlan network is working fine but it sounds like your chain is open and you need to add the resistor.

Have you disabled VATS and The Starter Checks with HPtuners.

You might have to ground one of the yellow starter wires. i am using most of the trucks wiring but remember reading about a similar issue on HPtuners forum. Search over there for e38 start issues.

TOOSLO5

Sorry, was reading your one post as series with the resitor in between rather than paralel with the resistors at the DLC end. This look correct? If so all I will need to do is add the resistors. With HPT VAT's has been disabled with the known good PCM and TCM but I did not disable anything with the starting checks. I will have to dig around HPT for some support also.

Thanks!

bsharpe

iTrader: (3)

ECM connector x1 pin 27(tan) goes to TCM Connector pin 11. ECM Connector X1 pin 28(tan/Blk) goes to TCM pin 10. From the TCM pin 13(Tan) goes to Pin DLC pin 14. TCM pin 14(tan/blk) goes to DLC pin 6. Pin 6 and Pin 14 of the DLc should be connected with a 120 ohm resistor. Both wires should be twisted together and be the exact same length.

This diagram doesnt have the Data lines but should help you with the rest of your wiring.https://ls1tech.com/forums/conversio...gram-here.html

TOOSLO5

Thanks! I will give her a try tonight and report back.

TOOSLO5

Update: Two things jack and ****!!!! I seem to have some sort of GM abortion that I cannot locate a pinout for. My TCM plug has something on pin 11 but nothing on pin 11. The majority of my wire colors and many of the pin numbers do not mach either. None of the T42 4L80E pinouts match what I have and maybe this is my issue. I will do some more digging tomorrow to find a pinout for the 80 and see if it matches the wiring info bsharpe was nice enough to supply.

TOOSLO5

Correction to the above. I have a wire on pin 11 but not on 10.

TOOSLO5

So I still cannot locate a pinout that matches my T42 plug but either way I did get the damn thing running last night. I located a tan and tan/black wire that was looped on the TCM plug that I cut and wired as Bsharpe said. This was a complete shot in the dark but it worked so I at least have that out of the way. Next issue to to try and figure out why the trans continues to show that it is in 2nd gear all the time no matter what gear it is in.