Aceshigh

2004 GTO LS1 harness modified by Speartech to go into a 78 Camaro.
I'm gutting my wiring harness, and putting in an American Autowire Highway 22 kit.

Now on to the question.
A shop did my install, and changed something on his modified LS1 harness....to get it working (allegedly)
Now what they changed, is they added a relay to a wire off the PCM.

I have zero clue as to what this wire does......so I took a few pics and I have the 5 pages of PCM pinouts
......but for the life of me CAN NOT find these wires in physical order.....on any of these sheets...

So I'm hoping someone here can tell me what this wire does and give me a sheet that shows me this to confirm it.
This is the wire, and I have no idea what bank or how to identify this yet.....





They wired up the relay like this.
30 = Ignition 12V (Should be pink from Speartech)
85 = Hot when brake pedal pushed down
86 = Ground
87a = Purple from PCM (Should be the purple from Speartech which actually goes to same purple wire)

If you count from LEFT to RIGHT as the picture angle shows.
It's the BOTTOM row, Pin #8

The first 2 wires
TOP ROW #1 is Grey w/ Blk stripe - PINS #3 and 6 = empty
BOTTOM #1 is Black w / Red Stripe - PINS # 2, 3, and 6 = empty

Now I labeled these when I took my OLD harness out.....but it's so jacked up I can't figure out what circuit is what.
Now John had a provision in his harness mod's for a Trans torque converter clutch operation off the brake switch......they didn't use it.
So I'm wondering if this is the same thing, but done a different way ???

Speartech

iTrader: (14)

Yes, that's pin 33, the TCC circuit. What you have described will work fine. If you don't have a 4 terminal brake switch (it's difficult to add on some applications) you can use a relay to serve the same function by wiring it up the way you have described.

By wiring the relay that way, you will have 12 volts on the TCC circuit when you turn the key on. When you apply the brakes the relay will trip, causing the voltage to drop to zero on the TCC circuit, which is exactly what the 4 terminal brake switch does.

Aceshigh

THanks John.

So I'll just reconnect the purple wire they cut into and get the 4 blade
brake switch you emailed me the link to and hook up your wires to it - Awesome.

richard_lyew

hi all, does anybody have the PCM/ECU/ECM pinout for the 1999 GMC Yukon Denali V8?