pcmhacking.net

hey probably a dumb question but i have made a standalone harness and getting to the point of kicking it over.
i have the p59 pcm and blue pin 39 is "start enable relay" how does this wire in when used with the PRND sw when no bcm is used? or is it even active with vats removed?
hope this makes sence.
cheers

On a GMT800 series truck, there is no direct interaction with the BCM for the NSBU switch. It all goes to the PCM first and if conditions are correct, it will enable the starter relay.. There is info on using Pin 34 as a clutch safety switch here https://lt1swap.com/2004vortec_pcm.htm

yeah thanks for the link. i had a play last night and from what i can see pin 39 does nothing when vats is off. prnd sw i wired in series with start relay and it cranks over no problems.
have a few little things to do before i can fire it so will keep on it and see if i have spark and injection.
cheers