Ford Mustang Forums banner
1 - 20 of 333 Posts

·
Registered
Joined
·
2,528 Posts
Discussion Starter · #1 · (Edited)
I have been getting tons of pms about this so I figured its time to make a post about it. Yes the Oxygen sensor harness has changed alteast 4 times that I know of and it can cause issues such as frying the trace off pin46 on manual ECU's or leaving you unable to pull codes in KOER if interchanged. The looped jumper wire for the NDS where it connects to the main harness is the difference. I have three o2 sensors harnesses here to show this but I need to confirm 2 of the harness years/ tranmissions since they got mixed up in a spare parts box. One of these is from a 91 5spd and the other I can't remember what I pulled it out of. I need to figure out which one is which first but I'll update it later when I do


If anyone has a factory aod or t5 87-93 mustang and can take a few pics of this harness it would be pretty helpfull, just list the year and transmission with a picture showing the pin location of the looped wire. The conector is located directly under where the factory mass air meter is mounted. Any way heres the pics of the ones I have just to show the differences.

90 aod harness



EDIT the one below with the purple/ yellow stripped looped wire is from a factory 1990 5spd car.
The blue / yellow stripped jumper wire matches the 02 harness in my 93 gt 5spd car



This is out of a 90 factory 5spd car so this does confirm NOT ALL 5spd harnesses are the same. I checked two friends cars that are both factory 1990 5spds.
 

·
Registered
Joined
·
5,338 Posts
I may be able to dig up some pictures of an 88 O2 harness by its self.............89 GT 5 speed harness, 93 GT aod harness, and 92 harness as well. althought it SHOULD be the same as the 93......... Ill try to do that sometime thisweek but my kid is due to be born............tomorrow or tuesday so i may forget, shoot me a pm if you don't hear back from me in a 'reasonable' amount of time. never had a kid before so #### may get crazy ;)
 

·
Registered
Joined
·
2,528 Posts
Discussion Starter · #3 ·
Take all the time in the world this is for other people so I don't get as many pm's from 3 or 4 year old posts lol. Theres too much misinformation out there so this is an attempt to put it in one place.

Congats on the kid btw.
 

·
Registered
Joined
·
2,528 Posts
Discussion Starter · #4 ·
still need to confirm the year and trans on the o2 harness with the blue/ yellow stripped wire.
 

·
Registered
Joined
·
270 Posts
The 88-90 manual/auto O2 harnesses were different from the 91-93 manual/auto O2 harnesses. Within each of those year groupings the manual harness is different from the auto harness in the location of a singe pin at one end of the 'loop' (jumper). All of this was because Ford used a different NGS circuit for each trans type.

From the info that I have been able to gather from harnesses I have:

88-90 AOD: jumper from pin 1 bottom row to pin 2 bottom row (as shown in the first picture)
88-90 5 speed: jumper from pin 1 top row to pin 1 bottom row (as shown in the third picture, left connector)

Pin 1 bottom row is the common end of the jumper.

I do not have specific pin/jumper location info for 91-93 O2 harnesses and know almost nothing about the 86 and 87 O2 harnesses.

Hope this helps some.
T
 

·
Registered
Joined
·
35 Posts
ok i'm not understanding...i have an 88 that originally had an aod in it. i yanked it out and put in a t5. does that mean i have to change something. or does this only mean if i'm trying to convert to mass air
 

·
Registered
Joined
·
5,338 Posts
this is sort of a 4cyl to v8 swap, need to know. Not needed with trans swaps.
 

·
Registered
Joined
·
3,486 Posts
The only time you will have a problem is mixing an AOD O2 sensor harness with the A9L computer. Using a 5 speed O2 hanress and a A9P will not hurt anything.
But again people will continue to fry them.

I think this thread should be made a sticky.
 

·
Registered
Joined
·
2,528 Posts
Discussion Starter · #12 ·
The only time you will have a problem is mixing an AOD O2 sensor harness with the A9L computer. Using a 5 speed O2 hanress and a A9P will not hurt anything.
But again people will continue to fry them.

I think this thread should be made a sticky.
You will also be unable to do a koer test since you will allways have code 67 and I beleive the circuit also ties into the cruise control for the clutch cut out. This is for people who want everything to work as if it where a factory 5spd car and to help the people who lost sig rtn on a 5spd ecu after doing a 5spd swap and computer swap.

Chad it does tie into a trans swap if you use a 5spd ecu.... I've helped alot of people chase this issue when they used an a9l ecu and lost sig rtn. Its just a reference post.
 

·
Registered
Joined
·
481 Posts
Rednotch:

If you feel like doing a little more investigating, could you check the ECU harness of each of those, and get wire colours that are getting turned around in there? That would be a help, eliminating more guess work.
I've got a mix-matched setup going into my ride as well.
 

·
Registered
Joined
·
235 Posts
this is what i know,does not matter what tranny you use,the harness is different between speed density cars and mass air cars
 

·
Registered
Joined
·
2,528 Posts
Discussion Starter · #15 ·
Rednotch:

If you feel like doing a little more investigating, could you check the ECU harness of each of those, and get wire colours that are getting turned around in there? That would be a help, eliminating more guess work.
I've got a mix-matched setup going into my ride as well.
I would if I could but both mustangs I own now are the odd man out 1990 so thats all I can provide info on. ford loved to change the wiring colors, locations and and pinouts on the fox body. Factory v8 fox body mustangs are a pita to find in any local pick n pulls anymore. There picked clean with in a few days of getting there so I dout I will find any other harnesses.

92notch306
Look at the pictures I posted there all from factory mass air cars, two from the same year, just ones an aod the other from a t5 car..... it does matter

You can get away with using either an aod or 5spd harness with an auto ecu but you will lose a few functions.... mix an aod harness with a 5spd ecu and you will get one dead ecu. Been there, done that, even helped more then a few people over the years with that issue.

http://bbs.hardcore50.com/vbulletin/showthread.php?t=44766 see post on hardcore50

same issue posted on corral

http://forums.corral.net/forums/showthread.php?t=751554&highlight=Exorcist
 

·
Registered
Joined
·
3,486 Posts
Red, I'm not sure why people are having such a difficult time comprehending this. You spelled it out plain as day. Trust me, I am by no means a wiring expert either.
 

·
Registered
Joined
·
5,338 Posts
You will also be unable to do a koer test since you will allways have code 67 and I beleive the circuit also ties into the cruise control for the clutch cut out. This is for people who want everything to work as if it where a factory 5spd car and to help the people who lost sig rtn on a 5spd ecu after doing a 5spd swap and computer swap.

Chad it does tie into a trans swap if you use a 5spd ecu.... I've helped alot of people chase this issue when they used an a9l ecu and lost sig rtn. Its just a reference post.
Holy crap, I think you are my savior. I pulled the AOD out of my GT years ago, and threw a 5 speed in along with a 5 speed harness. Ever since I have not been able to run codes.

Are you saying that Need a 5 speed o2 harness AND A9L computer or what? I haven't tried running codes in about a year and a half, but I swear I haven't been able to get the car to throw codes in years.......... Maybe I will go out into the garage after work today, since it finally warmed up, take all of the above pictures I said I would, and see if my car will run codes...........
 

·
Registered
Joined
·
3,486 Posts
AOD O2 harness and A9L/A3M computer = bad
5 speed O2 harness and A9P = will work (but again isnt correct)
If you are running O2's, you must match the o2 harness to the computer.
AOD harness/A9P
5 speed harness/A9L/A3M

DO NOT INSTALL ANY OLD O2 HARNESS ON A CAR WITH A A9L OR A3M COMPUTER. YOU WILL BURN THE BOARD. IF YOU ARENT SURE, THE YOU SHOULD CHECK YOUR O2 HARNESS CONNECTOR.
Just because things plug together doesnt mean all is well. As rednotch has stated over and over again. The o2 sensor harnesses are different because of the neutral start/safety circuitry that is part of them. If you do a trans swap such as AOD to 5 speed, then by all means just leave the AOD o2 harness and computer. Same with a 5 speed to automatic. Leave the 5 speed harness and computer. I am not sure who started the rumor that if you do a trans swap, you must swap the computer. I ran my current car with the A9P for a long long time after I did the 5 speed swap without issues. I have had quite a few others that were automatics with A9L's. Again no issues.
 

·
Registered
Joined
·
2,528 Posts
Discussion Starter · #19 ·
Holy crap, I think you are my savior. I pulled the AOD out of my GT years ago, and threw a 5 speed in along with a 5 speed harness. Ever since I have not been able to run codes.

Are you saying that Need a 5 speed o2 harness AND A9L computer or what? I haven't tried running codes in about a year and a half, but I swear I haven't been able to get the car to throw codes in years.......... Maybe I will go out into the garage after work today, since it finally warmed up, take all of the above pictures I said I would, and see if my car will run codes...........
You get no codes at all? or you can get codes in koeo but not koer because of code 67? how are you pulling codes, Jumper wire and cel light or scanner? Are both plugs at the clutch pedal switch pluged in or does one still have a jumper harness in it?

Try the jumper wire to pull codes threw the CEL light if the scanner won't comunicate and your getting no codes at all. STI to sig rtn on self test port. I have seen scanners not comunicate because of the nds circuit but was still ablle to pull KOEO codes threw the cel light.



if you still get nothing try the factory aod harness if you still have it and have the factroy aod ecu in the car. That atleast should allow you to pull codes, if not it sounds like you lost an internal ground in the ecu. you can check that by adding a ground to sig rtn and reruning koeo test... if you get codes its a ground issue.

While the t5 swap with an aod ecu and harness works Many people complain of idle issues and the cuise control not working properly when its done this way. The ecu uses both the ngs and vss to view load so with an aod ecu you get the hanging or high idle alot when coming to a stop and some get the rolling idle. Theres a reason ford used different ecu's for Autos and t5 cars and its not just because of the timing tables.


When I do a 5spd swap I change every thing now.... trans tunnel hump, t5 o2 harness from the same year, a9l and the t5 harness that runs from the drivers kick panel to the trans. thats the factory correct way. No idle issues, no butchered wiring, cruise control works like its supposed to and you can run both a koeo and koer test. The trans tunnel hump is so the lower shift boot will bolt up. Do you have too? no but if you want everything to work properly its the easist way to do it.





gnvair I remember when I first hit this issue craig couldn't pull codes from my car back in the late 90's I didn't find the cause till years later but I remember craigs scanner not even able to pull koeo codes... I was able to with a jumper but could never get past code 67 for a koer test.... the ngs was unplugged with no jumper so it was allways open, it had the aod 02 harness and an 93 cobra ecu in it at the time so it can be done... its just a half assed way to do it and you get a ton issues. Not to mention if someone Plugged the ngs in like I did when I put a a9l in it years later... poof fried ecu lol. Still have the repaired ecu in it now but all the correct harnesses from a 90 5spd car and every works like it's supposed to.
 

·
Registered
Joined
·
3,486 Posts
You get no codes at all? or you can get codes in koeo but not koer because of code 67? how are you pulling codes, Jumper wire and cel light or scanner? Are both plugs at the clutch pedal switch pluged in or does one still have a jumper harness in it?

Try the jumper wire to pull codes threw the CEL light if the scanner won't comunicate and your getting no codes at all. STI to sig rtn on self test port. I have seen scanners not comunicate because of the nds circuit but was still ablle to pull KOEO codes threw the cel light.



if you still get nothing try the factory aod harness if you still have it and have the factroy aod ecu in the car. That atleast should allow you to pull codes, if not it sounds like you lost an internal ground in the ecu. you can check that by adding a ground to sig rtn and reruning koeo test... if you get codes its a ground issue.

While the t5 swap with an aod ecu and harness works Many people complain of idle issues and the cuise control not working properly when its done this way. The ecu uses both the ngs and vss to view load so with an aod ecu you get the hanging or high idle alot when coming to a stop and some get the rolling idle. Theres a reason ford used different ecu's for Autos and t5 cars and its not just because of the timing tables.


When I do a 5spd swap I change every thing now.... trans tunnel hump, t5 o2 harness from the same year, a9l and the t5 harness that runs from the drivers kick panel to the trans. thats the factory correct way. No idle issues, no butchered wiring, cruise control works like its supposed to and you can run both a koeo and koer test. The trans tunnel hump is so the lower shift boot will bolt up. Do you have too? no but if you want everything to work properly its the easist way to do it.





gnvair I remember when I first hit this issue craig couldn't pull codes from my car back in the late 90's I didn't find the cause till years later but I remember craigs scanner not even able to pull koeo codes... I was able to with a jumper but could never get past code 67 for a koer test.... the ngs was unplugged with no jumper so it was allways open, it had the aod 02 harness and an 93 cobra ecu in it at the time so it can be done... its just a half assed way to do it and you get a ton issues. Not to mention if someone Plugged the ngs in like I did when I put a a9l in it years later... poof fried ecu lol. Still have the repaired ecu in it now but all the correct harnesses from a 90 5spd car and every works like it's supposed to.

Yeah I am not sure if you remember when I was ripping my hair out back in the fall with the issues I was having with my A9P. I actually did a search of your old threads and read through them again. Mad complete sense at that point. I was out of options and decided to repair one of the many "bad" A9L's that Craig had on the shelf since we were out of "good" computers. I repaired one of them and installed it in that car and it worked like a champ. I showed Craig the threads on what happens and he was amazed since we had sooo many cars come in with the TPS voltage reading 5 volts constantly (which is because all of the sensors reference voltage goes to a fixed 5 volt value when the trace fries). We have repaired several other computers now with great success. So yeah, I am a believer now. I am just not sure what killed my A9P. I rule out the O2 wiring since I havent had an O2 harness or O2's on my car in over 5 years.
 
1 - 20 of 333 Posts
Top