A9L 87 sd aod

mac_55

New Member
Nov 24, 2010
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Car 1987 mercury cougar speed density aod 5.0

parts---1989 a9l mass air conversion with h.o a9l

want to convert to t5 --89gt

i converted an 87 merc years ago from sd to mass with this computer and 89 h.o and never had a problem driving, burn outs fun times with an aod.

wanting to start all over again with rust free cougar and with doing so much reading my brain is scrambled eggs.

have been reading the 87 sd start neutral and clutch signals are + and ground, running a different path then the mass harness

-took my a9l apart just now and no visual burn traces anywhere on the board. (#46)

-dont have the looped o2 sensor harness

-will replace aod trans harness with t5 swap

from what i have been reading i was suppose to fry my ecm running it with aod , i know 88-93 ecms need to match the trans and o2 harness

Question

is this a sd harness thing that we can use either ecm or did i just get lucky,

sorry its long, someone please lay it out for me ,starting to dream of reading forums




Thank you
 
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Mstng93SSP

You have a nice rear end there Dave.
15 Year Member
Nov 29, 1999
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The ecm (ecu) does not know or care what transmission is in the car. The ecu are specific to the O2 sensor harness. So, if the car was an AOD with a factory AOD O2 harness, you need to use an AOD ecu A9P etc. If the car was a 5 speed and has a 5 speed O2 harness you need to use a 5 speed ecu A9L etc. The ecu only needs to match up to the correct O2 sensor harness. You can also repin either harness (AOD or T5) to match your ecu if you already had the ecu but the wrong O2 harness. In a nutshell, dont worry about what trans is physically in the car, only verify which O2 harness you are using and match the ecu accordingly.
 
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Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
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86-87 and early 88 cars do NOT have the looped harness at the O2 sensor. That only came on the late 88 and 89+ cars when ford changed to mass air. The wiring is different regarding pin 30 and keeping voltage off pin 46.

Therefore, no jumper to repin.

You are on the right track in installing the t-5 trans harness to hook up the NGS as this does affect idle quality and idle hanging. There is a benefit in swapping the ECU (and wiring harnesses) to match the trans as it will result in a better idle control when coming to a stop.

As a sanity check, remove the ECU and probe pin 46 to ground. Should be no voltage with key off, key on and during cranking. No voltage...slap the A9L in and you are good to go.

late 88 and 89+cars need to repin the O2 sensor harness. These early speed density cars aren't wires that way so no need. If you have a late '88 speed density car, then you do need to pay attention (like my car)
 

mac_55

New Member
Nov 24, 2010
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As a sanity check, remove the ECU and probe pin 46 to ground. Should be no voltage with key off, key on and during cranking. No voltage...slap the A9L in and you are good to go

just pulled the ecu plug and checked for ground, there is a black with white strip,

key off -- 0.000v

key run-- jumps to 0.100v then back to 0.003v

crank initial-- 0.080v then drops to .003 while cranking


so its a no go i guess with the aod and a9l

but once i change the trans harness and swap aod to clutch plug under steering dash it should fully ground ?
 
Last edited:

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
33,061
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Massachusetts
Not necessarily. By finding voltage on that pin, what I meant to say was 12v.

Sounds like you are good
 
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