WIRING by YEAR Gurus COME

[rustyruststang50]

how do I know what year wiring harnesses I have. I have my 91 gt interior and light wiring harness. that one doesn't have a fuel pump relay on it. can anyone tell me how to find out exactly by tear what engine harness I have? it has mass air and it has one black relay by the mass air plug. what else do I need to know to narrow down what year the engine harness is and to let me know if it will work with this 91 interior harness I have? any help would be great. plus I need some help identifying some of these other little harnesses/ components.

[rustyruststang50]

what are these components?

[TxFireman1972]

1987-1989-plug and play 2 connectors,1 black,1 gray

1990-year on its own- still has 2 connectors,one black,one gray,will physically plug into an 87-89 dash harness,but everything is wired differently due to the addition of the airbag circuits

1991-mid 1992- 1 reddish brown connector,fuel pump relay under seat

late 1992-1993- 1 reddish brown connector,fuel pump relay on computer harness, in engine bay, under MAF

the oxygen sensor harnesses are as follows:
87-89 auto
87-89 5spd
90-93 auto
90-93 5spd

using the wrong o2 sensor harness with the wrong transmission will result in a fried trace on PIN 46 of the computer. there is technically no difference in the dash or computer harnesses between an auto or a 5spd car. the difference is in the jumper wire on the o2 harness and the way that PIN 30 gets its ground thru the NSS on a 5spd car or starter relay on an AOD equipped car..using the wrong o2 sensor harness with the wrong transmission configuration results in 12v being sent to the SIGRTN as soon as you turn the key..fried computer..its repairable though

[rustyruststang50]

so if I am using 86 engine wiring harness is the 86 o2 harness the only one that will work for that year? and do you have the way to tell the difference between the harnesses

[rustyruststang50]

and mine has one relay by the mass air.

[86VertMK]

using the wrong o2 sensor harness with the wrong transmission will result in a fried trace on PIN 46 of the computer.

Just a bit of clarification for anyone who may read this down the road. I understood what you meant, but 6 months from now, someone else may not. The O2 harness should be matched with the ECM type (auto or manual), not the transmission type.

Niether the ECM or the O2 harness care what the transmission is, but the ECM really cares if it has the matching O2 sensor.

[TxFireman1972]

That's exactly right. Thanks for clarifying that. Sometimes I know what I'm trying to say, its just doesn't make its way on to the computer screen lol.

[ZephyrEFI]

what are these components?

The first two look like air bag sensors to me.

[Ourobos]

Read TxFireman's post, and then look at your main engine harness and see if it has an orange 8 pin connector, or two of them (black and a grey one). You either have a 90 or 91-92.5 harness.

And on the O2 and ECU deal.. I'll note you CAN run an automatic computer on EITHER harness, but can only run a manual computer with a manual harness, put a manual computer on an automatic harness and it'll fry the signal return circuit, due to grounding differences.