Dear friends,

Does anybody know whether an PCM from a 95 Cougar (V8) can be used on a 94 Cougar (same engine)? I only have a shop manual for my Cougar (94), but not for the 95 donor car, so I've no way to compare the PCM pinouts and specs on the two cars. The cars were manufactured five months apart, but are different MY ... Is there a place where I can cross-check PCM versions for compatibility?

The 95 ECU I harvested from the junkyard is
- F3SF-12A650-DA (fw rev A5W0, manufactured 09/12/94)

The 94 ECU on my car is
- F3SF-12A650-AD (fw rev E4A3, manufactured 04/20/94)

I can post the 94 pinout from the 94 EVTM - in case someone has the 95 pinout for comparison. Thank you, and Happy Thanksgiving!

Cheers,
cougar_fan

 

I would say yes, since I'm the one that got you into trouble on this. Most of the difference is in calibration (in '95, they added the misfire monitor). If you look at the part numbers, both are F3SZ prefixes, and that's the right prefix for Birds. Anytime for reflashes a pcm for anything, the pcm PN changes to reflect this. The most important thing to go by is calibration numbers. They won't match from year to year, but some of my friends in parts can chase the number changes back through the years. I deal a lot with this kind of crap, because no one else will. Another thing in your favor is this: most of the 104 pinouts are the same from year to year. For example, I have a 8 cly. PCM i use as a tester, it's just that the other 2 injectors and coils aren't there, even though the drivers are wired into the PCM. THe biggest thing to look for is engine size, major harward differences (COP vs. Coil pack), and PATS or No PATS. Let us know, please!

 

Come on, greasemark, you didn't get me into any trouble at all, on the contrary, you and hanky are helping me out of the trouble here!

I checked on Motiorcraft's website last night for the latest calibration data for the 94 and 95 PCMs and, although the part numbers are different (F5SF instead of the F3SF I have on the car), the hardware revisions are identical for both MYs. I stretched another $40 for a 95 EVTM, when that'll get in I'll compare the pinouts on the two PCMs ... I'd rather make sure I don't toast anything else on the car by swapping the boxes.

I couldn't find any mention about PATS on 94 or 95 MYs, apparently the MN12-based Cougars never got this. However the donor Cougar had Traction control (which means ABS as well, right?) while mine doesn't have either. Could this be a problem? I know that ABS is controlled by its own hardware, but I wouldn't be surprised if Ford would have programmed the PCM to do some engine magic during ABS kick-ins, to reduce the stress on the transmission. I'm just fantasizing here, please feel free to bring me back on Earth . I just don't want to do more harm to my car ...

Thanks again!

Cheers,
cougar_fan

 

Oh ... I just realized one more difference between the two boxes: the 95 PCM is likely from a Canadian Cougar while mine is certainly from a US model... I wonder if there are differences in calibration depending on which side of the border the car was shipped to ... similarly to the differences between California vs the 49 states versions. Juts a thought...

Cheers,
cougar_fan

 

Okay, I wasn't the clearest on my last post. The pinouts ARE all the same, or so close that it won't matter. The ABS does concern me, as this was the first of the "self aware" (even if crude) networks, where the ABS and PCM were in bed together. If I remember correctly (and this is a lot of alcohol ago, so DON'T hold me to it), the ABS and T/C might have been programmable options. As far as hardware is concerned, I don't think you have anything to worry about; but, when i get to work in the morning, I'll pull up the pinpouts to be sure (they have a nicer computer). It's always been a problem with calibrations with these. The good thing is, they're all sealed, so no revisions are needed. As for PATS, I also should apologize that these never had PATS (I think the '97 Expedition was the first to use it), so don't worry about it. California calibrations were also very good, especially for the emissions, however, they run a little leaner, and seemed to lack a little power.
One other thing sticks out in my mind about these platforms. They were an old design that was moderately upgraded, but there was a TSB about if you had the latest calibration, then you needed new injectors and some kind of valve body upgrade with different springs that made it shift slightly differently. I'll try to see if i can find it also. However, as most of the trannies have been rebuilt by now (several times), i don't think it would be an issue.
One other thing to keep in mind. Whatever you wind up using, the calibrations are all done, so whatever you get will most likely wind up being a late '95 calibration, and you'll have to use it anyway. In '96, they added a few more monitors (EVAP, catalyst, and o2 and o2 heaters, if my memory serves correctly.) But don't worry, if it's from a similar car, then the reflash (if needed), was simple.

 

Interesting points - thank you! Weirdly enough, no matter how hard I try, I don't remember seeing the ABS pump on the donor car ... the engine bay was laid out exactly like my Cougar's ... so it could be that the T/C button on the dash monitor module may have been there just for the looks of it, although, yet again, the car had rear disk brakes - typical for ABS-equipped Cougars/Tbirds. I'll run to the junkyard on Saturday to clarify (and rip more useful pieces out of that carcass :-)

On a different note, the BOB seems to have finally made it to my post office ... I'll pick it up tomorrow - then, boys and girls, let the fun begin

Will keep everybody posted. Greasemark, thanks again for your help on this one. Should I ever come to Denver, I'll make sure I'll stop by to have a beer (or two, or more) with you.

Cheers,
cougar_fan

 

And you really have to look for the HCU, as it's under the battery tray and probably eaten to death by battery acid. Have fun with BOB! Let us old farts know what's up.

 

... I thought it was the BOB in the mail, but it actually was the exact replacement PCM I bought a while ago ... darn, will have to wait a few more days. For now, I won't plug any of the spare PCMs until I get the BOB and verify that the wiring is fine ... don't want to toast my spares.

If it turns out to be a wiring problem (open or high resistance circuit) BETWEEN THE SENSOR AND THE PCM CONNECTOR: what if I unplug the left O2 sensor and connect the right O2 sensor outputs to both inputs on the PCM on the BOB? This should fool the PCM into thinking that both sides work identically, so it will drive the fuel/air ratio on both banks according to the good-reporting sensor. True, there won't be any averaging between the two banks anymore, but since the engine is symmetrical (... and mine is in very good shape, 49kmiles), the whole engine will flow between slightly rich and slightly lean, without going into deep lean mixture as it does now, based on readings from both sensors. Long shot, but hey, you never know ...

Please let me know what you think. I will, of course, keep you posted, this turns out to be a great learning experience for me and, hopefully, for many other people reading this forum.

Thanks again,
cougar_fan

 

You know, you have a really good handle on this, and good instincts. As the resident Senior Master Tech that has tried to explain this to you (and all), you've lowered yourself to my standard of "What does the processor need to be happy." I'll warn you about this now, as you'll actually drive yourself crazy thinking about this all. And I DON'T show the colors of the title often, as I can still stub my toes with the best of them.
I wouldn't recommend the O2 rewiring for 2 reasons. One, it isn't the way the car was made, which brings us to two, the PCM is most likely looking for 1) That specific o2 to send a rational signal, 2) the heaters for the o2 are controlled by EEC, which uses the heater control (internal to PCM) to turn on and off the heaters during the o2 and o2 heater test (software, based in the pcm, and executed only whent he executive diag. monitor wants it to run), and 3) yes, the engine is symmetrical, however, for the minute differences of spark duration, injector balance, and general combustion of the mix on whatever bank it is, the long and short term fuel trims may/cannot compensate for whatever variables are present on that bank of the engine.
The other thing this can do is create another lean misfire, if the injectors, plugs,wiring, and air/fuel mix are not perfectly calibrated. The opposite is also true. And now you've bumped right up against the never really mentioned aloud, but tactitly understood fact that these engines run just about at the point of a lean misfire all the time, and only minute adjustments to the air/fuel mix keep it running well at all (as evidenced by the rough running, missing, etc when your car is not running right). Physics is a bitch, and you can't change it.
My experience tells me that you're very technically minded, and you've explained that very clearly in your posts. I believe you've exhausted the wiring angle on this pretty well, however, BOB will be the final test. There should be no shorts or opens to either ground or power or any other wire if the wire your testing goes back to the pcm for component control. In other words, the injector drivers, o2's, o2 heaters, etc., all need to have good wiring; and wiring problems are where many, many good techs can fall down, as it is sometimes impossible to find exactly the spot where a problem is. Or, at least not without taking the entire loom apart to find it, and that creates other problems. To wit, I had a car not too long ago that had several strange tranmission problems, but only when in 4x4. I traced it back to a missing Signal REturn circut, which is the PCM ground for just about every sensor (trans sensors, o2's, ect, iat, etc.). I would've much rather have stared at the sun through a telescope then trace this out (which i did find and fix, luckily). However, to give you an idea, on this car, Sig. Return branched to about 25 other points, and as this opened up intermittanly, and only in 4x4, the possibilties of me finding the open were diminishing rapidly.
One other thing before I go to work. There are times when you have to take a chance (kinda like having kids, I suppose). But only when your reasonably sure that whatever your diagnosing is working the way it should, and isn't contributing or causing the said issue. It is also possible that you have 2 different problems that are working together to cause said problem. It's rare, but it keeps me on my toes. Good luck!

Mark

 

Thank you kindly for the reality check, Mark ... you read me right: I have this foolish tendency to become impatient at times, and start cutting corners when I'm almost there ... which made me screw up things quite a few times in the past. It's obvious that Ford wasn't about making more money out of us when they decided to double the number of oxygen sensors on the V8s. It's just my crappy human nature showing off here

I'll keep everyone posted. Thanks again!
Dan