Hi, I have an 87 Trans Am 305 TPI with the digital GTA style gauges that i am in the process of switching over to a carbed 400, I was wondering what wires I will be able to unhook from the computer and still have the gauges work?

I would like to get all the unneccasary wiring out of the way but I would rather not hack up the wiring harness, I thought maybe I could just unplug the tires at the computer and take them all out but it seems like I will need to let one of the plugs hooked up on the compter in order for my odom to still function, If i unplug one of the plugs the odom lights up but if i unhook the other one the odom shuts off will I just need to let the one hooked up and then I can follow the other set of wires out through and remove them all together or do I need to have both of them??

I take it my odom reading is saved in the computer??

any help is greatly appreciated

 

As I understand it, the speedometer is a separate module from the engine control module. However, I have no personal experience with that.

The under-hood harnessing that you don't need will go to the passenger side fenderwell. The things you will need - ignition power, tach wire, alternator wiring, temp & oil pressure gages, starter wires - will separate out from the ECM harness. Start by getting the things you will need labeled and separated, and you should be able to take the rest of it out in one piece. Take the plastic fender liner out to get access to the ECM pass-through connector.

I'm not completely sure about the radiator fan wiring. I believe that can be separated out as well.

 

Thanks alot five7, but now I got some more questions, lol


I was trying to seperate the oil pressure sensor wire from the harness and it is a white wire but then it runs to a plug which also has a green wire in, what did this originally connect to??

Should I just cut the plug off and splice the green wire and the white wire together??


What relays do I need to keep? Aren't most of them for heater and headlights??

What does the tach wire look like??

 

I know that the tach wire will be white, and the oil pressure sending unit will be a tan wire by itself. The other connector going into where the oil pressure is, should be orange and then tan with a white stripe which is for the fuel pump relay to tell the computer if the oil pressure drops below a certain point it shuts the fuel pump off to keep from blowing up the engine.

 

when I put my carbed 383 in my Trans Am one goal was to eliminate any wire under the hood that did not have any purpose. what I did was label all the needed wires before I removed the old engine, temp, oil pressure, starter, alt, etc. then I removed the ecm harness. to remove the harness I started inside the car by unpluging it (under the pass side dash) and then pulling it through the kick panel area then up through the pass fender till it was finally in the engine bay. then I started unpluging every single sensor and a/c wire related to this harness. DO BE CAREFULL don't cut out any wires unless you are 100% sure you will not need it. when I was done I had eliminated I would say prob 90% off all the wiring under my hood, yep 90% and I still have my pop up headlights, running lights, alt wires, starter wires, guages, and window wiper wires. you would be surprised at how many wires really you will not need after you are done eliminating them. the only relays I still have are the ones for the pop up headlight motors but thats it for relays.

 

How do I get the clip apart that goes around all the wires that run into the passengers side of the dash?? I got it popped out of the car but I can't get it to split open and don't want to destroy it.

if I wasn't a damn idiot I would have also labeled eveything before I pulled the motor, but of course that just would have made things too simple!

 

where the ecm harness goes through the kick panel, it is actually 2 plugs right there for the ecm if I remember right. the harness's are held in place by a clip that is very similar to a c-clip. the clip is U shaped when you get it off, the bottom of the harness is where the open part of the clip would be, make sense lol. anyway with a flat screwdriver pry the clip towards the dash pad and it will eventually pop off. when it comes off then you can start to feed the harness through the fender and into the engine bay. kind off tedious, it took me 4 hours to get the one out of my latest parts car b/c I wanted to sell the tbi setup with a complete harness. it may seem like the harness won't fit through the top of the fender well but it will, one plug at a time. (2 plugs)

 

I'm going carb but just wanting to get the engine harness unplugged so I can get the car painted. How do I remove this connector? I haven't tried from under the dash.

 

That's not really a "connector", it's really just a bushing kind of thing to clamp the wires in place and seal up the interior.

On the inside, there's a sort of horshoe-shaped plastic clip that goes around the outside of it. The clip slides off, then the wiring can come out of the car through the hole.

 

I guess what I'm asking is can I leave this intact and still remove the harness? I don't want to destroy it.

 

You can leave that intact and remove the connector from the outside. You can't really take the wires out from the inside and leave that plug there.

 

It is part of the harness; it must come out with the wires.

If you remove the clip, it comes right out. Just reverse the process of factory installation. That harness came to the assembly plant as part of the engine, and was installed into the car as it rolled down the production line. No need to destroy anything at all.

Use some Window-Weld and sheet aluminum or some such, to cover up the hole in the cowl after you remove the plug.

 

What I was saying is you can remove the engine compartment harness from the other side and leave the pictured connector/plug/bushing there along with the harness (which goes to the ECM). You aren't really gaining anything by removing it, and by removing it you have a hole in the body to plug.

But, your statements are correct if you want to remove the interior harness pieces as well.

 

I don't intend to leave the harness out. I just want to remove it to do the body work. Then I figure out what I need and don't need to go to carb. I intend to keep the ecm in the car. This is my first project like this so I'm learning as I go. Thanks.

 

I got the harness out. I guess I should have been looking instead of typing. Thanks for the heads up on the C clip.

 

Education is typically a mix of what others tell us and what we find out on our own. The nice clear in-focus pic you posted will probaby come in handy for educating others in the future - my car body is black, and the connector wouldn't show up very well in a picture.

I discovered in my quest that the '82 and '86 connectors were different sizes. My first attempt was to take the '82 connector apart to see if I could use that "bushing" for the '86 harness. Gave up pretty quickly on that and took a file to the kick panel hole instead. Having the fender off (it was FUBAR, a new one was on the way) made that process much, much easier.

 

Ahhh, the learning process. I learned that if you remove ALL the wires from the pass. side, you will no longer have a heater. Not fun in February. No, not at all.