Electrical Speed Density 02 Harness on Mass air car??

sav22rem22

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Feb 6, 2020
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Hello all. It's been a while since I've posted last but since we last talked I've put on some new battery cables along with a new IAC. I checked my 02 sensor harness the other day as I'm going over the whole car and I noticed that it appears to be a speed density harness and there is no way to pin it out. This is strange because my car is an 89 and obviously mass air. I do believe however that at one point it was swapped from an AOD to a T5. I'm having very many weird idle issues and generally just not having a great time with the car. Would this speed density 02 harness cause any issues and should I get an 02 harness for my year and make sure it's pinned out correctly? When I do this should I go ahead and make sure that I have a manual transmission harness while I'm at it? I don't want to burn the computer up. I'm also not totally sure if the NSS is being used or not and I'm not very knowledgeable about anything to do with the trans harness. So what should I do? Thanks for any help
(Quick Edit) I forgot to mention that the car now has an A9L in it. When I bought the car the inj and main harness were cut up and the ecu was a C3W1. Not sure if any of this helps or matters.

5A7D4F69-C2FA-4A19-844C-6E5A4026B16E.jpeg
here’s a picture of the 02 harness if that helps. I do not see a place to put the jumper for my year and transmission
 
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Mustang5L5

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Feb 18, 2001
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Look on the opposite side of the plug for the jumper. The speed density harnesses were 5-wire and came on the 87 and early ‘88s. By late 88 all cars had the 7-wire harness plug there with jumper.

From the pic, it looks like 7 wires
 

fox racer v2

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Jun 2, 2019
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Here's the stock '89 T5 plug wiring, the 'loop' or bridge are the teal dots (will be different on AOD). White is left unused (again, AOD will be different), the purple/pink are consistent on between SD/MAF setups (87-93, at least. Not sure on '86):
O2 harness.PNG


Best bet to verify the wires, colors may change through the year so could be indicative of someone swapping an old one out for a different one.

If the computer is fried the car may still start but run super rough. Report back any codes you may have
 
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sav22rem22

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Feb 6, 2020
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Teal is manual trans.

Auto loop would be the white to the teal below it
Great information as always. Thanks fellas. Now that I look at my picture I do see that it does appear to be a mass air harness but the jumper doesn’t look jumpered in the right place. I’m assuming I shouldn’t touch the jumper until I confirm that I have a manual transmission harness in the car? I think it’s still an aod trans harness because I can start the gear in gear and no clutch down at all. I can still dump codes without the code 67 as well and I can’t find the plugs that may have been jumped for the clutch safety switch
 

sav22rem22

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Feb 6, 2020
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Alright p
Here's the stock '89 T5 plug wiring, the 'loop' or bridge are the teal dots (will be different on AOD). White is left unused (again, AOD will be different), the purple/pink are consistent on between SD/MAF setups (87-93, at least. Not sure on '86):
O2 harness.PNG


Best bet to verify the wires, colors may change through the year so could be indicative of someone swapping an old one out for a different one.

If the computer is fried the car may still start but run super rough. Report back any codes you may have
I actually dumped the codes yesterday and what it came back with was my usual code 22 for bap sensor failure and then a bunch of evr smog related codes. I did get a code 33 because I have no vacuum line hooked up to the egr. (Not done by me). I also passed the cylinder balance test. This is my second bap sensor on the second harness. Albeit the second bap was also used and given for free as a test. But besides high idle issues the car actually runs pretty good now.
 

Mustang5L5

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The two plugs that connect to the clutch pedal switch are buried up in the dash wiring near the clutch pedal. They are there, but depending on how the dash harness was installed they may be tucked in a way that they are hard to see. If you can't find them, pull the driver's seat, get comfy, and really stick your head up in that area and search for them.

They look like this. Black one is the start circuit and is jumpered here to allow an AOD to start without pressing in a pedal

p2190037-jpg.jpg


They plug in here (except obviously not cut)
p2190036-jpg.jpg
 

sav22rem22

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Feb 6, 2020
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The two plugs that connect to the clutch pedal switch are buried up in the dash wiring near the clutch pedal. They are there, but depending on how the dash harness was installed they may be tucked in a way that they are hard to see. If you can't find them, pull the driver's seat, get comfy, and really stick your head up in that area and search for them.

They look like this. Black one is the start circuit and is jumpered here to allow an AOD to start without pressing in a pedal

p2190037-jpg.jpg


They plug in here (except obviously not cut)
p2190036-jpg.jpg
Ah okay thanks so much. So I know where at least one is (the clear one)Now I just need to find the black one and I’m sure mine is jumpered otherwise I don’t think my car would start. Then on to identifying the trans harness if I could find it in the mess that’s under my dash. Quick question, if my computer can’t detect that the car is ever in neutral, wouldn’t my idle logic change and have a bit of a hanging idle since the car thinks it has a bit of load?
 

Mustang5L5

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Yes, that’s exactly what would happen. Hanging idle.

Check the door tag. It will tell you if the car was originally an AOD. If it was, you are likely missing the connector for the NGS on the t5 and will need to change that harness
 

sav22rem22

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Feb 6, 2020
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Yes, that’s exactly what would happen. Hanging idle.

Check the door tag. It will tell you if the car was originally an AOD. If it was, you are likely missing the connector for the NGS on the t5 and will need to change that harness
I’ll check out the door tag tomorrow. Hopefully it’s still there. Also another question and sorry if it’s a stupid one but where does the trans harness plug into the actual car at? Thanks for all the help this far.
 

Mustang5L5

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It goes through the trans tunnel on the drivers side, then under the drivers seat, then to the drivers side kick panel.

My car was an speed density AOD. I went to 5-spd mass air. I had to change the trans harness and repin the o2 harness
 

sav22rem22

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Feb 6, 2020
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It goes through the trans tunnel on the drivers side, then under the drivers seat, then to the drivers side kick panel.

My car was an speed density AOD. I went to 5-spd mass air. I had to change the trans harness and repin the o2 harness
Ah okay so I was probably staring the plug right in the face then. Strangely enough me just touching wires made all sorts of funny things happen with the car. The passenger window won’t roll down anymore and then the right hand blinker would blink but wouldn’t show up on the cluster so I messed with the physical blinker and it started working again. I have no idea what kind of hack job the previous owners did but it sure is taking its toll on me lol. Thanks so much for the help
 

sav22rem22

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Feb 6, 2020
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It goes through the trans tunnel on the drivers side, then under the drivers seat, then to the drivers side kick panel.

My car was an speed density AOD. I went to 5-spd mass air. I had to change the trans harness and repin the o2 harness
I think I’ve identified everything. The black plug that plugs into the clutch safety switch is for some reason plugged into something else which is some plug that runs up to a black box under the dash. The transmission harness is for an aod and the 02 harness appears to be pinned out for an aod although I could be wrong. There also appears to be another 02 harness just sitting there that is pinned out for a 91-93 T5. I’ll completely verify the 02 harness that’s on my car tomorrow in better weather but would my computer already be burned up if it was pinned out for an aod? My car runs okay besides the hanging idle and probably a few vacuum leaks but all voltages check out. Does the 02 harness pin out depend on the type of transmission harness in the car?
 

Mustang5L5

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Mod Dude
Feb 18, 2001
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O2 harness depends on the ECU. Pin it to match the ECU, but you should change the harnesses to All match as well. If the car is a stick, run a 5-spd ECU and harnesses.

All over the net you read that ECU chNges for 5spd swaps are optional, but my car finally ran the best once I actually did it. Too many hanging idle nuisances with the Aod stuff after going 5spd
 

sav22rem22

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Feb 6, 2020
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North Carolina
O2 harness depends on the ECU. Pin it to match the ECU, but you should change the harnesses to All match as well. If the car is a stick, run a 5-spd ECU and harnesses.

All over the net you read that ECU chNges for 5spd swaps are optional, but my car finally ran the best once I actually did it. Too many hanging idle nuisances with the Aod stuff after going 5spd
Hm okay. Hopefully there isn't any damage done to my computer. Hopefully a correct trans harness and a correctly pinned out 02 harness will at least fix some of these hanging idle issues. It wont be perfect until I get a new BAP sensor but at least it's a start. Thanks for all the help this far!
 

fox racer v2

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Jun 2, 2019
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Hm okay. Hopefully there isn't any damage done to my computer. Hopefully a correct trans harness and a correctly pinned out 02 harness will at least fix some of these hanging idle issues. It wont be perfect until I get a new BAP sensor but at least it's a start. Thanks for all the help this far!

If it’s not obvious in how the car runs, check codes. I fried my a9p, and the car idled at 2,500 rpm and raised when put in gear (very obvious things were wrong). If you did fry your computer, check the ecm harness before installing the next ecm:

With no ECM plugged in, connect the battery. Put key on. Check for voltage on Pin 46 of the ECM harness - there should be none. Have a friend turn the key to start and check pin 46 once again, there should be no voltage. This is the only sure fire way to know you won’t burn up the next ecm the same way you did the last. This would also lead you to believe the o2 loop is wired correctly.

Edit: overlooked your other response - leaving above for reference.
 
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sav22rem22

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Feb 6, 2020
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North Carolina
If it’s not obvious in how the car runs, check codes. I fried my a9p, and the car idled at 2,500 rpm and raised when put in gear (very obvious things were wrong). If you did fry your computer, check the ecm harness before installing the next ecm:

With no ECM plugged in, connect the battery. Put key on. Check for voltage on Pin 46 of the ECM harness - there should be none. Have a friend turn the key to start and check pin 46 once again, there should be no voltage. This is the only sure fire way to know you won’t burn up the next ecm the same way you did the last. This would also lead you to believe the o2 loop is wired correctly.

Edit: overlooked your other response - leaving above for reference.
Okay thanks for the info. I honestly have no idea how it's not fried right now but I will do the pin 46 test once this weather clears up. If pin 46 had power wouldn't my sigrtn trace be fried and I wouldn't be able to dump codes?
 

fox racer v2

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Jun 2, 2019
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Okay thanks for the info. I honestly have no idea how it's not fried right now but I will do the pin 46 test once this weather clears up. If pin 46 had power wouldn't my sigrtn trace be fried and I wouldn't be able to dump codes?

That’s exactly what would happen - but my experience is that codes will still be able to be run. I fried pin 46, if I ran codes 3 times I’d get a different combo of the same half dozen or so codes (random combos of everything grounded on pin 46). Point being it’ll be obvious, if your consistently gettin MAP/BAP only (22 is it?), it might just be coincidence not necessarily indicative of a fried ECM.

When its little gremlins like you’re chasing, I find it easier/cheaper to eliminate everything you can, and fix only what you can’t.