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Electrical O2 harness repin

  • Thread starter Thread starter Mustang5L5
  • Start date Start date Jan 27, 2019
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Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
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Jan 27, 2019
#1
  • Jan 27, 2019
  • #1
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. See post 15 as to what the jumper should be repinned to.

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


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


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



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


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.



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.
 
Last edited: Sep 14, 2023
Reactions: Steel1, fredfifty, Flatfoot and 1 other person

JD1964

there is enough sticking out to grab on to
15 Year Member
Jun 28, 2013
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Jan 28, 2019
#2
  • Jan 28, 2019
  • #2
Nice work and good pictures. Mr Moderator, you should sticky this
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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Jan 28, 2019
#3
  • Jan 28, 2019
  • #3
I pm'd fastdriver, I'll check back later
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,167
17,862
224
Massachusetts
Jan 28, 2019
#4
  • Jan 28, 2019
  • #4
I asked noobs to add it to the technical thread index that is already stuck
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
27,829
10,509
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polk county florida
Jan 29, 2019
#5
  • Jan 29, 2019
  • #5
I see noobz did it, I didn't want to screw it up but I see he already did.
 

Alley Oop

Member
Mar 29, 2017
71
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18
West Coast of Canada
Jan 29, 2019
#6
  • Jan 29, 2019
  • #6
In my humble opinion, it is a sticky.
 

fredfifty

5 Year Member
Nov 23, 2011
318
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59
SF Bay Area
Jan 30, 2019
#7
  • Jan 30, 2019
  • #7
a good site to go to as well www.ponyperformance.com > technical.> 88-93 oxygen sensor harness identification
 
Reactions: Potomus Pete
R

rwatts

Member
Jul 7, 2015
21
3
13
Feb 4, 2019
#8
  • Feb 4, 2019
  • #8
Mustang5L5 said:
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


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


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



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


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.



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.
Click to expand...
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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Feb 8, 2019
#9
  • Feb 8, 2019
  • #9
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.
 
Reactions: Noobz347 and General karthief
R

rwatts

Member
Jul 7, 2015
21
3
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Feb 10, 2019
#10
  • Feb 10, 2019
  • #10
jrichker said:
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.
Click to expand...

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.
 
Reactions: Noobz347

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,167
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Massachusetts
Feb 10, 2019
#11
  • Feb 10, 2019
  • #11
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
 
Reactions: Noobz347

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor
Admin Dude
Jan 4, 1985
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Feb 10, 2019
#12
  • Feb 10, 2019
  • #12
jrichker said:
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.
Click to expand...
rwatts said:
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.
Click to expand...
Mustang5L5 said:
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
Click to expand...

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

rwatts

Member
Jul 7, 2015
21
3
13
Feb 11, 2019
#13
  • Feb 11, 2019
  • #13
rwatts said:
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!!
Click to expand...

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

10 Year Member
Feb 28, 2003
904
5
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Feb 1, 2021
#14
  • Feb 1, 2021
  • #14
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?

 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,167
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Massachusetts
Feb 1, 2021
#15
  • Feb 1, 2021
  • #15
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
 

5.0 Nostalgia

10 Year Member
Feb 28, 2003
904
5
39
CT
Feb 1, 2021
#16
  • Feb 1, 2021
  • #16
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.

 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,167
17,862
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Massachusetts
Feb 1, 2021
#17
  • Feb 1, 2021
  • #17
You are correct.
 

5.0 Nostalgia

10 Year Member
Feb 28, 2003
904
5
39
CT
Feb 2, 2021
#18
  • Feb 2, 2021
  • #18
Mustang5L5 said:
You are correct.
Click to expand...
Thank you again!
 
F

Fox2newedge

Member
Feb 13, 2024
24
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Laurel, Florida
Jul 22, 2025
#19
  • Jul 22, 2025
  • #19
Hey all! I'm sorry for re-energizing this thread, but have a question I'm hoping someone can help me with.
I'm helping a friend mass air convert his '87 GT that was originally equipped with an AOD. We T-5 converted the car and have an A9L. He purchased the Pro-m mass air conversion harness and have installed it.
However the O2 harness does not have the jumper loop to repin it.
What needs to be done to the '87's O2 harness so as to not burn out any traces in the ECM? Anything at all?
Thank you in advance!
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,167
17,862
224
Massachusetts
Jul 23, 2025
#20
  • Jul 23, 2025
  • #20
The 87 doesn't have the jumper. Wired differently than the 88+ cars with the jumper.

So sanity check, before you plug the ECU in, use a meter on the 60-pin connector. Touch pin 46 to ground and turn the key to ON and then to crank. Should not get voltage.
 
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