Hey all,

I have my MAF converted 302 up and running, and while I'm ironing out a few issues, I decided to go ahead with an A9L and Quarterhorse to get everything out of my build.

Right now its running very rich, and while I'm struggling to KOER pull codes, I figure the (hopefully functional) A9L might put out the codes.

I've been reading that there is a possibility of frying the ECM if the O2 is wired incorrectly...

So with this being an A9L from a 90' and my harness is existing from the 89 F150, what do I need to do to ensure the O2 will work, and also no fry my new ECM?

Thanks all,

Glaser67

 

Just make your truck pinout match the A9Ls (I'm assuming you have the pinouts if you've gone this far).

Make sure you don't put +12v to the O2 signal, and I think you're fine.

 

Hopefully you didn't just plug the A9L into a totally unmodified '89 truck harness.

 

Hopefully you also opened the case in the A9L PCM and looked the board over.

I have "3" Mustang PCMs.
A9L
A9P
C3W

All had capacitor failures.... green corrosion and leaking capacitors on the board.

Just a heads up on your MAF conversion.

 

I followed the diagram below for re-pinning the 89' 302 SD harness to match the "re-manufactured" unknown MAF ECM, see picture and diagram below. Yes it does run and is drivable despite the pig-rich condition. The fact that it runs off the generaic computer leads me to believe the O2 wiring is good or at least wont fry my ECM, but now we're talking about an A9L...






NOTE: I jumped the O2 output signal wire from 29 across 43 or vice-versa. This MAY be a problem, I know you all will tell me it's OK or that I need separate sensor inputs: I'll get to that later




I had to cut the seal to open this up to inspect. Vendor tells me it's out of a 90 GT.




If i didn't know any better, I'd say this looks OK





To clarify, I did modify the existing 89' harness to the Mustang MAF pinnout, and it is drivable, I just want to make sure I don't fry the holy grail of stock mustang ECM's when I plug it in. I will make verify no +12 volts to the signal before I connect it. My hope is that besides minor performance and tunablity, this verified ECM will output KOER codes for further diagnostics. If I'm no worse off with my rich condition, the Quarterhorse aught to tell me what going on.

Furthermore, what has me confused are these Mustang forums talking about modifying SD Mustang harnesses and overlooking the O2 signal output, but I think if I follow Lead Heads advise by verifying no +12V to signal, I aught to be alright.

As I work this out, I'll report back on my results, and as always, this communities $0.02 are always welcome, that's why we're all here.

Thanks guys!
-Glaser67

 

Look Again....closely...

The 2nd pic, with the capacitor near the interface for the Quarthorse tuner, shows it has already leaked brown goo.
That capacitor has failed.

Also, in the 3rd pic, the capacitor near the edge of the board appears to be failing. There is goo near the area of it.

Save yourself some time, effort, and sanity and replace those capacitors.

I didn't know how bad mine was until the truck wouldn't idle in park in 10°F weather. Keep telling me the ACT sensor was bad. Then, when it would reach 30-40°F temp, the truck would smooth out.

"An ounce of prevention is worth a pound of cure"

 

[QUOTE=timbersteel;16557340]Look Again....closely...

The 2nd pic, with the capacitor near the interface for the Quarthorse tuner, shows it has already leaked brown goo.
That capacitor has failed.

Also, in the 3rd pic, the capacitor near the edge of the board appears to be failing. There is goo near the area of it.

Save yourself some time, effort, and sanity and replace those capacitors.

I didn't know how bad mine was until the truck wouldn't idle in park in 10°F weather. Keep telling me the ACT sensor was bad. Then, when it would reach 30-40°F temp, the truck would smooth out.

Wow, it seems obvious now...OK I'll take care of them, am I correct to assume that an electronics repair place would know how/what to replace them with?

Given how easy the ECM is to replace, this weekend I'll run the A9L before I get it repaired, just as a control and to prove you right!

While I'm at it I'll have my muffler shop weld a 2nd bung on the driver side collector and add the 2nd 02 sensor...I know there's a lot of back and forth about this issue, but I really don't think it would hurt anything by adding the 2nd one as it was designed to be.

Thanks,

-Glaser67