Help identifying Ford Authorized Modification to PCM back in '97

[olympic]

Hey everyone, I have a '96 GT Convertible and recently changed the 3.08 gears to 3.73. I just picked up a SCT X4 7015 tuner so that I could correct the rear axle ratio. The issue here is that I plugged in the SCT and it detected it was a Mustang. I selected the pre-programmed option and then the 4.6L option. It brought up a few things I could change (interesting that tire size and axle ratio were not in the list of options - my reason for buying this). Anyhow, when I tried to save the tune it gave me an error, 110BE - Unlock PCM Failed. Odd, the car is stock. In doing some research online there seemed to be indication that even a change by Ford can lock the PCM. I recalled seeing something stuck to the top of the radiator shroud and sure enough it is a sticker labeled "FORD AUTHORIZED MODIFICATION". Below that the writing is pretty worn off but I can make out "Reprogrammed PCM". There are a couple of lines below it, the first only has a handful of letters and is difficult to make out. Looks like: H*PRZ. The line below that has more letters, here's what I can make out:
FU2F ***A850-GE.

The asterisks denote a character that I can't make out and the ones I can could be wrong but those are my best guess. Shows the date performed as 10/20/97.

Does anyone know if there was a recall or TSB back in '97 for the '96 that would have resulted in this PCM modification?

The car was originally my dad's and he owned it since new and I inherited it when he passed. I will call the Ford dealer that was local to him but not sure if they will have records from 23 years ago. I'm curious what this modification was.

I'll also be reaching out to SCT to see if they have any knowledge of this and to confirm whether or not their X4 device supports changing of the gear ratios for the 1996 Mustang GT which was the entire reason I purchased this tuner.

 

[lwarrior1016]

I’m sorry to tell you this, but on cars up to 98, the tuner does nothing for tire size and gear ratio. The speedometer is not controlled by the ecu until 99. You have to get a different gear for the speed sensor or you get a speedcal box and wire it in.

I am also no help with the Ford program question.

 

[olympic]

Thanks for that info lwarrior1016, although that news isn’t what I wanted to hear. Do you know if the gear change has any impact on the transmission that I shouid be concerned about? Had read somewhere in the forums when changing the gears that it can impact something about shift points and the PCM should be tuned to account for that. Perhaps it doesn’t apply to ‘96. I plan to run it down the 1/4 mile once in awhile just for fun so want to make sure that if I leave it alone or decide to put in a speedcal or different speed sensor gear that everything else should be okay as is.

I’m also curious with the car basically stock if there is really much benefit from this SCT X4. It’s plastic and probably floats so it’s not even worthy of boat anchor status. Thanks.

 

[07GtS197]

If you don’t retune first the steeper gears you’ll get stacked shifts. Otherwise it won’t have a truly negative effect as far as I know but it’ll shift into overdrive pretty early unless you’re in the throttle. You might as well keep the tuner as you can use it down the road when you get your issue figured out. Maybe you could swap the ecu?


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[olympic]

If you don’t retune first the steeper gears you’ll get stacked shifts. Otherwise it won’t have a truly negative effect as far as I know but it’ll shift into overdrive pretty early unless you’re in the throttle. You might as well keep the tuner as you can use it down the road when you get your issue figured out. Maybe you could swap the ecu?

If the tuner doesn't account for gear ratio changes any idea how I tune to avoid the stacked shifts?

 

[07GtS197]

In the meantime you can’t.


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[olympic]

In the meantime you can’t.

Once I have the speedometer fixed with a speedcal or speedometer gear, will I then be able to use the SCT X4 to adjust shift points? Trying to make sure I understand whether I can fix the stacked shift issue with the gear change once the speedometer has been addressed. I am not sure on the '96 what the computer factors into the shift points.

 

[lwarrior1016]

So the transmission speed sensor goes in to the ecu (it’s a sensor on the side of the trans, not the output by the driveshaft) that reports what the transmission rpm is and the tuner should fix the shift points based on what you put in the computer (I think). But the ecu does not control the speedometer. The speed cal will fix the speedo but have no affect on shifting.

I hope this is clear enough.

 

[07GtS197]

The ecu controls the transmission so the speedcal will have no effect. The ecu will have to be either unlocked or replaced and a tune installed.

Edit: Beat me to it

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[olympic]

So the transmission speed sensor goes in to the ecu (it’s a sensor on the side of the trans, not the output by the driveshaft) that reports what the transmission rpm is and the tuner should fix the shift points based on what you put in the computer (I think). But the ecu does not control the speedometer. The speed cal will fix the speedo but have no affect on shifting.

I hope this is clear enough.

Okay so I need to fix the speedometer but it's really a separate issue from the transmission shift points. For the shift points it sounds like the SCT tuner may be able to assist but it sounds like it will be a manual process since it doesn't have a way to adjust based on the gear ratio. I'm still trying to understand, does the PCM tell the trans when to shift and if so what exactly does it base that on? Is it based on rpm or speed? I'm trying to understand so that I can figure out how the gear change is impacting the transmission shift points and understand what I will need to adjust in the tune accordingly. I don't know if the gear change results in "short shifting" by the transmission and if that is what I will need to address. Thanks for the help.

 

[olympic]

The ecu controls the transmission so the speedcal will have no effect. The ecu will have to be either unlocked or replaced and a tune installed.

Sounds like I still need to get the PCM unlocked by Ford so that I can use the tuner. I'll call the dealer tomorrow to see if I can find any info about what the modification might have been and what they will charge to flash it back to stock.

 

[07GtS197]

Good luck getting that info, I don’t mean to be a Debbie downer but I doubt they’ll have that info.

I’m not sure how to answer that, the ecu should get the vss signal for the transmission. There are many factors that go into transmission shift points. Speed, rpm and load are all factors.


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[olympic]

Good luck getting that info, I don’t mean to be a Debbie downer but I doubt they’ll have that info.

I’m not sure how to answer that, the ecu should get the vss signal for the transmission. There are many factors that go into transmission shift points. Speed, rpm and load are all factors.

I'll see what I can find out about the old PCM modification. I'm trying to understand how the gear change to 3.73 will impact the shift points. I was thinking that it would still shift at the same RPM points. Granted, it should reach those RPMs a bit more quickly with the gear change. So what I'm trying to understand is why the trans will supposedly shift at a lower rpm....if I'm understanding the issue correctly. Thanks for continuing to explain this to me.

 

[07GtS197]

When you swap to steeper gears your driveshaft/engine spins faster for any given speed than before. So it’ll shift at the same rpm but lower speed. So it’ll short shift gears.


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[olympic]

Okay. I will tackle the speedometer issue first. Is it easy to replace the speedometer gear? In doing some research looks like the one I need is DOOZ-17271-B, 21 teeth purple. If I'm understanding correctly it involves removing the VSS and then switching out the gear that is attached to it and put it back in. Doesn't sound too bad, maybe I'm missing something? I've read that sometimes the VSS will get stuck in the trans. Trying to decide between this approach and a speedcal.

 

[07GtS197]

Do the speedcal, it’s more money but you won’t have to screw with the trans at all. I swapped the speedo gear in my 87 Grand Marquis so I know its not hard but imo the speedcal is more handy and versatile.


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[olympic]

Here's an update on my saga for those following along at home. Called dealers but they don't carry records back to 1997 so hard to say why the PCM was reprogrammed but was told too that the Ford Authorized Modification sticker was the standard way that the dealers would indicate if the car had been updated. I was told that this update shouldn't "lock" the PCM and that it should still be able to be married to the SCT X4. I chatted with SCT and they aren't sure what the issue is. I will try a device firmware update and need to verify voltage is at least 11.7 (it was showing 11.87 so should be good there).

With regards to the speedcal I see that the Ford Racing version has been discontinued. I liked the idea there of the underhood approach. In the meantime I ordered a purple 21 tooth gear and plan to try this route. It looks like it's a matter of unbolting and pulling out the VSS, unclipping the current gear and using the new one.

I'll post updates as I progress through it.