cal30_sniper

iTrader: (16)

Hey all,

I'm midway through a V8 swap on my roommate's 92 V6 Firebird, and I've run into a bit of a dilemma. I'm attempting to use an '88 TPI engine harness that I got off of craigslist to wire the engine bay side of the wiring, as well as the ECM side. However, it appears that sometime between '88 and '92, the pinout for the C100 bulkhead connector changed.

On both my '88 GTA, and the spare '88 TPI harness that I have, the windshield wiper motor and windshield washer motor come off of the larger side (engine harness) of the C100 connector to the driver's side of the engine bay. However, on the '92 harness that came in the car, the wiper and washer motors come out of the smaller half (front light harness) of the C100 connector on the passenger side of the vehicle.

I have both halves of the harness from the '88 car, so I can just replace the entire C100 connector, including the engine wiring and lights/body wiring completely. However, I'm betting the pinouts for the engine side of the firewall are not going to match the interior side of the harness. I have the '88 Service Manual diagrams, which match up with what I'm seeing on the spare '88 harness, as well as the harness in my GTA. I don't have any diagrams for the '92. Does anyone have a '92 factory service manual that they can upload pictures of the c100 connector pinouts? If I had the '92 pinouts, I should just be able to repin the interior side of the harness to match the engine side (or at least be able to tell if I can run some kind of halfbreed combination of the two halves of the harness, I know a lot of pins aren't always used).

Thanks for the help guys! I'm including the photos I took of my '88 Service Manual so y'all can see what I'm looking for.

Dyno Don

iTrader: (7)

You really need to get a '90-'92 harness and ECM, it is a nightmare to use anything else.

cal30_sniper

iTrader: (16)

Been digging through the '88 Manual and some 92 wiring diagrams on Austin Third Gen, and I'm beginning to come to the same conclusion.

It looks like I can reuse the 92 V6 harness for lights/wipers/washers. I should be able to connect the 88 Engine harness at the C100 connector by changing the following:
1. Brake Warning Light (tan/wht) moves from B2 on the '88 Harness to the A5 slot going into the '92 connector.
2. Charging System (brn) moves from F8 on the '88 Harness to the G8 slot going into the '92 connector.
3. Fuel Pump Relay (Red) at E6 on the '88 Harness has to go somewhere, can't find the equivalent on the '92 diagram?

That leaves the C207 connector, and the ECM connections. I see several mismatches at the C207, and I haven't begun to dig into the ECM connections yet.

If I could figure out the C207 connector, and I use an '88 ECM, wouldn't that allow this to work with the C100 modifications I listed above? The harness we have is complete, and I'd really like to use it. I also have all of the tuning stuff for the 165 ECM already, and I have experience tuning MAF, where I have zero experience tuning SD.

Is it really going to be that hard, or is this doable? I just can't understand why GM would change all the pinouts from year to year, it just doesn't make sense.

cal30_sniper

iTrader: (16)

Also, would it be an option to source an '88 Fuse/Dash wiring harness and install that in the '92, and then use the '88 engine and lights harness unmodified? I already have the interior ripped apart for the T56 swap and a heater core change, so it wouldn't be that hard to replace the harness while I was in there.

-cal30sniper

Dyno Don

iTrader: (7)

Those two dashes are not compatible, connections are different.
'86-'87 harnesses are the same, '88 is by itself as is '89.
'90-'92 are the same.
You can't even put the '88 dash in as the framework is different.

cal30_sniper

iTrader: (16)

Wow, learn something new every day. Doesn't make any sense why they would change it so often, but I guess there's a lot of things in the automotive world that don't make any sense. I always thought the only difference was the layout of the harness when they went to serpentine in '88, and the ECM and ECM pinouts when SD came around in '90. I had no idea that the C100 and C207 connectors don't interchange.

Looks like I can get my hands on a '92 TBI harness fairly cheap. I'll probably just snag that and splice in the extra injectors from the '88 harness, as well as the few other modifications that need to be made to convert to TPI. I guess that '88 harness is about to become the donor for the LQ4 swap on my GTA.

Thanks for the help!

-cal30sniper