So far this is the best detailed wiring diagram I can find

http://chevythunder.com/19992002_ls1...agrams.htm#PCM Power and Grounds

The 5th and 6th diagram from the top looks like its for the OBD2 connector used for tuning and reading codes.

So...I have the ls1 in the ram and I need to be able to have it tuned, and read codes, today I tried hooking it up but had no communication with ECM.

Looks like I need 4 wires for the OBD connector, orange is power, 2 separate grounds(black), and then the (Purple wire used for communication??)

Since I do not have a underdash harness I tried to just run off the purple wire from the engine harness from the 2001 camaro. with this and power/grounds I have my scanner powered up, but no communication still.

Now on the 6th page it looks like there is a splice pack (SP200)....? do I really need this for the scanner to read the computer?

 

Looking on the 6th page again it looks like the communication wire coming FROM the ECM is dark green.....? not purple.....It turns into purple AFTER the splice. Maybe this is my problem...I'll have to try this tommorow as the truck is at my dads house where my shop is.

Unless someone else thinks otherwise I'll try the dark green tommorow

 

There are alot of wires that have the same color but do different jobs in these harneses. I'm looking at the wires that go through the fire wall on a 2001 camaro on the passenger side.

 

So I tried the dark green wire today and it worked....but only with key-on, When the truck is running it loses comunication. I wonder if there is something with the BCM that's messing with things.

 

There was a MIL code for malfunction in the SES light circuit. I hooked up a small light and sure enout it was on . I cleared the codes with key on and the light turned off, but still with the truck started it loses comunication.

 

Not sure why you are losing the data stream with the engine running. I found this slightly more detailed diagram:

 

Moved from Advanced Tech.

 

Since the circuit is so simple go back to the basics and ignore the body connectors where the correct wire may or may not be. Go strait to the PCM B58, snip the lead and solder a new lengthening onto it. Run this to the ALDL ppl

The 12v and grounds can come from anywhere, this is the only critical wire in the connector. If you still loose serial data then there is something SERIOUSLY messed up in the harness

 

I'll try that, but if it doesn't work, then there may be something up with not running an BCM or instrument cluster....?

Either way once i figure it out I'll post up

 

Running a BCM on a swap car is extremely rare. I highly doubt it's causing your problems

 

i am having the same problem in my 01 trans am i check my sp200 splice mine code reader with give me on code then says err1 havent had any luck with it yet.. but my cluster on has power on half of it dont know why that are if it could have anythang to do with it ????