How BCM controls things? VY commodore

[evilstuie]

Hi Guys,

I'm starting to install a dash/body harness from a VY commodore into my LS1 PCM controlled SBC400 motor in an 85 TransAM with VY dash transplant and have hit a bit of a wall.

When I took the harness out of the donor car, I had to cut the wires heading towards the back of the car, and the wires heading to the front of the car from the engine bay fuse box.

At the time I thought I could just sit there for a day or so with a multimeter from the fuse boxes to the wire ends and figure out which wire needed to go where from the fuse diagrams... that doesn't seem to be the case, and I'm assuming it's all thanks to the BCM.

From what I gather the BCM is a glorified Relay controller that takes a signal from a switch, for example brake light, and when that grounds (or gets voltage) however it works, it then sends a signal out a different wire from the BCM to energise that circuit.
My question is, how can I figure out which wire is coming/going to which?

And am I on the right line of thought with how the BCM interacts with everything?

[Micks]

Basically...but doubt it switches brake lights as there is no secondary need for the bcm to do this. The only way to marry up the harness is to cut the shit outta of it you don't need or build your own. At the end of the day are you gunna need a full VY harness in your build anyhow?

[evilstuie]

BCM would need the brake signal for cruise control etc, so that's why i was thinking they would go through it as well, and I tested for the brake light wire on all connectors and loose wires but couldn't find it.

I figured I might as well try to use as much of the VY wiring as possible, as I've already got the 0411 LS1 PCM, the VY LS1 harness repinned for SBC firing order, the BCM, the gauges, and dash controls in the car. and it'd be easier to wire that all in than seprately. Plus the car's wiring was going on 30 years so i figured time for a refresh anyway.

[Micks]

Will you be using the bcm? Next bet is get your hands on a VY wiring diagram, plenty getting around. :yup: