Electrical/engine bay harness questions

djj62478 · May 29, 2026

So I have a 90 GT and recently did some engine bay work to. Needless to say I pulled out the wiring harness and now putting it back in I have a few questions. First off does anyone have a diagram of the harness routing like on the firewall around the strut towers where the headlights section goes , etc, etc. Also does anyone have a diagram of what connectors go where I pretty much have them all plugged in like the obvious ones but there are a few that I'm not sure about and also one or two wires that are broken. Lastly the routing of the starter wire and where all the engines ground mount to. Thanks in advance.

Willybill32 · May 30, 2026

djj62478 said:
So I have a 90 GT and recently did some engine bay work to. Needless to say I pulled out the wiring harness and now putting it back in I have a few questions. First off does anyone have a diagram of the harness routing like on the firewall around the strut towers where the headlights section goes , etc, etc. Also does anyone have a diagram of what connectors go where I pretty much have them all plugged in like the obvious ones but there are a few that I'm not sure about and also one or two wires that are broken. Lastly the routing of the starter wire and where all the engines ground mount to. Thanks in advance.

I believe the routing and connector layout is shown in the EVTM (Engine Vacuum Troubleshooting Manual) which you can generally find on eBay. I have an ‘86 EVTM, but they’re year-specific.

Bill

KRUISR · Jun 2, 2026

I have my 90GT here in my garage and can look where anything goes. I am also currently putting my son's 89 GT back together and might be working on the same connectors.

Which connectors are you looking for? Pic and current location on harness would be helpful.

Starter wire goes down from starter solenoid, under the engine between the crank pulley and front sump of oil pan. Main ground wire follows it and connects to timing cover on driver side. Pic below is where that wire connected when I was disassembling my motor 11 years ago.

You can see the starter cable bracket and where the engine ground attached. The other main engine ground is a braided cable from the back of the driver side head to the firewall.

Looks like there are 2 grounds. The braided one is broken off here but you can see the clip still attached.

djj62478 · Jun 3, 2026

Thanks kruisr. These are the wires im taking about. First picture is by the mass air connector, second is attached to the headlight section of the harness, third is coming off the harness of the injectors, fourth is separate with that pigtail broken wire, fourth is near the coil area and finally there's this other one with that rubber section in between that's also a separate one.

KRUISR · Jun 3, 2026

From pic 3 and using my photo here as reference, I think those connectors go to the Purge Cannister (connector front left of pic), the Engine Coolant Temp sensor (middle) and the IAC (barely seen just to the right of the middle connector).

In pic below I am pointing at the Purge Cannister connector and the second pic is where it goes to.

For Pic 1, how many wires go into that connector?

Pic 4 almost looks like an O2 sensor sub-harness, not sure which side. But I could be wrong.

Pic 2 - is it for the horns?

Pic 5 - if your connector looks like this...

That connector goes to the AC Clutch connector.

Pic 6 and 7 - I haven't figured out what they are, but that looks like a diode in the middle.

nicholase · Jun 6, 2026

6 and 7 are the AC clutch sub harness.

nicholase · Jun 6, 2026

Pic #4 is the o2 sub harness like @KRUISR pointed out. The cut tan wire is for the oil level sensor in the oil pan. So that's the drivers side of the harness and the drivers side o2 connector.

Pic #1 plugs into the o2 harness. Should have 8 pins.

djj62478 · Jun 6, 2026

Is it possible to still use the starter harness with one of the metal ends broken off? The driver side metal bracket is broken off. Should I just get a new starter harness?

Electrical/engine bay harness questions

djj62478

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Willybill32

But at least it's tight!

KRUISR

djj62478

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KRUISR

nicholase

I lubed and pushed, until it was all the way in

nicholase

I lubed and pushed, until it was all the way in

djj62478

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Electrical/engine bay harness questions

Member

But at least it's tight!

Member

Attachments

I lubed and pushed, until it was all the way in

I lubed and pushed, until it was all the way in

Member

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