Electrical ECU Questions

Old Catman

Member
May 24, 2020
12
2
13
76
central florida
I am installing a 90 5.0 and AOD in a 66 Mustang. I bought a wrecked 90 mustang 5.0 with a 5 speed and swapped over all the wiring, sensors, dash cluster, steering column and the A9L ecu. So electrically it is a 90 mustang without the air bag stuff. I have read many posts about going from aod to manual with no problem, but I don't find any going from manual to aod. My question is will the A9L work with the aod? What about idle when stopping in gear with the load from the converter and transmission?

I am not using the smog pump or vapor canister but I kept the EGR. Will any of that give me a check engine light?

If I can use the A9L I will send it to ECU Exchange to go thru it. Or do I need to find a A9P instead?

I would love to have kept the t-5 but my left knee doesn't like pushing a clutch pedal anymore.
 
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HemiRick

I'd be looking at jacking under the house
Jun 28, 2020
730
274
73
57
Memphis TN
A9P is the auto trans ECU the a9L will work if the O2 wires are changed.....there's some diff between the auto and manual O2 wiring.
 

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
36,124
12,040
224
Massachusetts
The least hassle way to do it is to use the AOD ECU and repin the O2 harness to ‘90 Auto wiring. I mean that in terms of chasing potential issues down the road.

you can use the A9L but you might have some idle hang issues or stalling. The way the 5-spd ECU and auto ECU manage idle strategy is slightly different. Something to consider with the fact that the AOD is loaded up ehen at a stop.

if it was my car, I’d sell the A9L, buy an A9P, and repin the o2 harness to the correct auto wiring. The NGS connector that plugs into the switch on top of the T5 will hang empty now. Test pin 46 on the ECU connector for voltage before plugging in the ECU.

no air pump or vapor canister will generate codes but not a CEL. No effect on how engine will run.
 

Mustang5L5

i'm familiar with penetration
Mod Dude
Feb 18, 2001
36,124
12,040
224
Massachusetts
O2 sensor pinouts


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