converting 99 v6 firebird to a formula thanks to the donor motor and trans from my camaro. I have a 2000 Z28 wire harness and pcm. the interior harness is from a 2000 ws6. I was told that the relay harness aka the under hood harness must also be swapped. the car wont start. I can jump the starter relay box by touching 30 to 87, but the car wont key on. I spent two days trying to figure out why, I disconnected the yellow and black wire from the pcm and grounded it. still stuck

 

Making the same thread twice in the same section won't resolve your issue, try the the advanced tech forum or the PCM tuning diagnostic forum.

 

i did an ls1 swap on my 98 bird and used the v6 harness under the hood with the ls1 harness on the engine, runs like a dream