Electrical O2 harness repin

Mustang5L5

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This thread is a HOW-TO for the process of repining the o2 sensor harness to match ECU/Trans, in the event the car is swapped. Please do not ask me what the harness should be repined to. The information is out there in an easy google search.

Step one. Remove the o2 sensor harness from vehicle. I find it easier to do on a bench plus it allowed me to degrease and reloom the harness. You can do this in the car if you want...it's that easy.

Here's the default loop setup in my 1988 AOD car
IMG_2478.JPG


First you need to remove the red clip. Lightly pry up with a small pick
IMG_2484.JPG


Next, look down inside with a light and you'll see small plastic tabs that secure the pins. Gently pry away from pin with your pick and pull the pin out

IMG_2486.JPG


Pin fully removed. You really only need to take one side oit
IMG_2488.JPG


In the new location, press through the rubber backer with your pick to poke a hole through. Doesn't take much effort.

Then, push the pin through and all the way in until you hear a click.

IMG_2489.JPG


Reinsert the red clip and you are done. Above is new location for my car running a 5-spd trans and ECU.

And that's it. Takes 5 mins to do. You can easily do this in the car if you wanted to as well. The connection is located underneath where the MAF sensor is located.
 
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rwatts

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This is more of a how-to as to the method of repinning the o2 harness jumper. As to where the pin goes on AOD vs 5-spd, please consult other sources as it differs from year to year

Step one. Remove the o2 sensor harness from vehicle. I find it easier to do on a bench plus it allowed me to degrease and reloom the harness. You can do this in the car if you want...it's that easy.

Here's the default loop setup in my 1988 AOD car
IMG_2478.JPG


First you need to remove the red clip. Lightly pry up with a small pick
IMG_2484.JPG


Next, look down inside with a light and you'll see small plastic tabs that secure the pins. Gently pry away from pin with your pick and pull the pin out

IMG_2486.JPG


Pin fully removed. You really only need to take one side oit
IMG_2488.JPG


In the new location, press through the rubber backer with your pick to poke a hole through. Doesn't take much effort.

Then, push the pin through and all the way in until you hear a click.

IMG_2489.JPG


Reinsert the red clip and you are done. Above is new location for my car running a 5-spd trans and ECU.

And that's it. Takes 5 mins to do. You can easily do this in the car if you wanted to as well. The connection is located underneath where the MAF sensor is located.
I am pleased with your post very much!! Can you help me with some info on using an A9L PCM with an AOD? Pin 30 gets the start signal on a A9P with auto. Does the A9L need the 12 VDC start signal to when used with an AOD?
Thanks very much!!
 

jrichker

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The A9L is not compatible with an auto trans.
Put 12 volts on pin 30 for an A9L and you will damage the computer. It burns up the trace for signal ground for all the engine mounted sensors. It will also prevent you form being able to dump the codes.
 
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rwatts

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The A9L is not compatible with an auto trans.
Put 12 volts on pin 30 for an A9L and you will damage the computer. It burns up the trace for signal ground for all the engine mounted sensors. It will also prevent you form being able to dump the codes.

This is true if you do not repin the o2 sensors. there is no way pin 30 goes to pin 46(ground) when using an auto with an A9L PCM, when following prints by Ford Technical Dept. This drawing shows 12volts on pin 30 when starting on both the A9P an A9L. This is why you must repin the o2 sensors when doing this swap unles you have the correct o2 sensor harness.
 
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Mustang5L5

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That's why I repinned mine.

Originally a speed density AOD car.

Swapped to 5-spd, added the 5-spd trans harness and swapped to mass air using an A9L. Had to repin
 
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Noobz347

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The A9L is not compatible with an auto trans.
Put 12 volts on pin 30 for an A9L and you will damage the computer. It burns up the trace for signal ground for all the engine mounted sensors. It will also prevent you form being able to dump the codes.
This is true if you do not repin the o2 sensors. there is no way pin 30 goes to pin 46(ground) when using an auto with an A9L PCM, when following prints by Ford Technical Dept. This drawing shows 12volts on pin 30 when starting on both the A9P an A9L. This is why you must repin the o2 sensors when doing this swap unles you have the correct o2 sensor harness.
That's why I repinned mine.

Originally a speed density AOD car.

Swapped to 5-spd, added the 5-spd trans harness and swapped to mass air using an A9L. Had to repin

These three posts are a good explanation of what must be done, when, and why. :nice:
 

rwatts

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Jul 7, 2015
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I am pleased with your post very much!! Can you help me with some info on using an A9L PCM with an AOD? Pin 30 gets the start signal on a A9P with auto. Does the A9L need the 12 VDC start signal to when used with an AOD?
Thanks very much!!

Again, thanks very much for all the info. Do you know of a person or site to go to for an answer to my question?
 

5.0 Nostalgia

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Feb 28, 2003
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Great thread and great how to. Just have a couple questions that I still can't seem to get through my head. I am restoring a '91 notch that was originally an auto (now a T5). I put an A9L in it from a friend's '89GT I parted. Before finding this thread, I was going to use the O2 harness from the '89 GT. At some point I misplaced either the that harness or the original harness from the '91 auto. Now I only have the one attached. I am almost certain it is from the '89GT and the pinning seems to prove that. My questions are why would a '91 5.0 have a different pinning than the '89 5.0? Did they come with a different computer? And most importantly, is the harness pictured therefore pinned correctly for a '91 5.0 with a T5 and an A9L even though it doesn't conform to the diagram below that shows the jumper pinned to 1 and 6?

IMG_9190.jpeg
Capture.PNG
 

Mustang5L5

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The reason the pins are different us because of the wiring changes year-by-year for the Fox. There are subtle changes throughout the 87-93 run. I believe the harnesses are broken down this way: 87-early 88, late 88; 89; 90; 91-92 and 1993. That's why it's always best to keep your harnesses the same year.

If this car is a 91, and has 1991 body and engine harness, then you should pin it for the 91. Yes, you can use the 89 o2 harness in this case, but the jumper needs to reflect the 91-93 pinout. You'll also want to verify the wire colors of the harness matching the wire colors on the body harness.

ALWAYS verify no voltage on pin 46 on the ECU connector (with the ECU out) by testing while crank and the key to ON.

ANother graphic showing the same as above
1612210075160.png
 

5.0 Nostalgia

10 Year Member
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Thanks so much for the reply. That makes complete sense now. After reading your response I decided to go out to the garage and search all my boxes for the harness from the '91. I ended up finding it in the one box that wasn't labeled! From what I am gathering, I need to move wire in the top left corner down to the bottom left corner. Would that be correct? The attached picture is upside down compared to the diagram.

IMG_9192.jpg