Intermittent DTC 647...incorrect third gear ratio.

[J.Rovirosa]

I'll apologize right off the bat for how long this is, but I'm trying to be as detailed as possible

Replaced the trans. in the '95 around 75K miles ago with a Ford remanufactured unit. Since then, roughly every ten thousand miles I'll get the flashing OD light and corresponding rough up/down-shifts. Still shifts into every gear, even overdrive, when this happens. Disconnect the battery for a half hour to clear the code and everything is back to normal until it happens again. Thought nothing of it because it was easy enough to circumvent, fluid level never changed, and it always looked good and was flushed or changed every 20K miles.

Earlier this year, I installed a bunch of goodies I bought to shore up the trans: Transgo shift kit, Superior boost valve, what I "thought" was a new EPC solenoid, and a few other common v.b. mods I discovered here. Also flushed the fluid using the cooler line/bucket method and installed a new Magnefine filter. The trans. went back together perfectly and shifted great, but I've now got the OD light again, which I just found out indicates a problem with the third gear ratio.

Searching for the code, I found out that it may have something to do with a TSB for the '95 model computer that alters the shift characteristics of the trans. To my knowledge, this TSB was never performed on my Ex.

Can anyone with a similar situation that has had the processor replaced comment on whether or not it addressed the issue? And is there anything I might have overlooked....should I be looking at anything else as the culprit?

Thanks

EDIT: while searching for "647" I noticed that this code pops up most frequently in the '95 Explorer; literally every other thread was started by the owner of a '95. This leads me to believe the PCM update for the '95 is likely the problem.

 

[swetrid]

Needs a new pcm if you want code to go away. Here is the tsb.
Printable View (10 KB)
TSB
98-5-16 TRANSMISSION - 4R44E/4R55E - O/D OFF LAMP FLASHING AND/OR DIAGNOSTIC TROUBLE CODES (DTCS) 645, 646, 647, 648 STORED IN MEMORY

Publication Date: MARCH 16, 1998

LIGHT TRUCK: 1995 EXPLORER


This TSB article is being republished in its entirety to update the Service Procedure.

CALIBRATION:
5-58B-R10, 5-58R-R10

WARNING: THIS MODIFICATION IS AUTHORIZED ONLY FOR THE LISTED ENGINE. PERFORMING THIS MODIFICATION ON OTHER ENGINE CALIBRATIONS IS UNAUTHORIZED AND COULD CREATE LIABILITY UNDER APPLICABLE FEDERAL OR LOCAL LAWS.



ISSUE:
Some vehicles may experience a flashing "O/D OFF" lamp and/or the following Diagnostic Trouble Codes (DTCs) may occur: 645, 646, 647, 648. This may be caused by a damaged intermediate and/or overdrive servo piston seal, faulty Throttle Position (TP) sensor wiring or a concern with the transmission control strategy.

ACTION:
Follow the diagnostic procedures listed in the 1995 Explorer Service Manual and the following text for details.

Service all non-transmission DTCs and concerns first.

Service all transmission DTCs and concerns except for DTCs 645, 646, 647, 648.

For the above DTCs, follow TSB 97-17-24 making sure that the Electronic Pressure Control (EPC) solenoid is functional, transmission bands are adjusted properly, and the servos are not damaged.

Check the TP sensor wiring, wiring crimps, and peform a wiggle test.

If after checking the transmission and TP wiring no problems were identified, verify the vehicle has the latest level calibration. If it does not, replace the Powertrain Control Module (PCM). Refer to the following PCM Application Chart for correct PCM usage.



PCM APPLICATION
Old Calibration Old Part Number (-12A650-) New Calibration New Part Number (-12A650-)
5-58B-R10 F5TF-ARC 5-58B-R10 F5PF-BRA
5-58R-R10 F5TF-ATC 5-58R-R10 F5PF-BSA


Obtain an Authorized Modifications Decal (FPS 8262 - obtainable through DOES II, 25/pkg) and list the date, dealer number, and summary of modifications performed. Select a prominent place adjacent to the Vehicle Emission Control Information Decal suitable for installing the Authorized Modifications Decal. Clean the area, install the decal, and cover it with a clear plastic decal shield.




PART NUMBER PART NAME
F5PZ-12A650-BRA Powertrain Control Module (PCM)
F5PZ-12A650-BSA Powertrain Control Module (PCM)



OTHER APPLICABLE ARTICLES:
95-19-12, 97-17-24

SUPERSEDES:
98-3-21

WARRANTY STATUS:
Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage

OPERATION DESCRIPTION TIME
980516A Replace Powertrain Control Module (PCM) 0.3 Hr.

DEALER CODING
BASIC PART NO. CONDITION CODE
12A650 42

OASIS CODES:
206000, 501000, 504000


--------------------------------------------------------------------------------

Copyright © 1998 Ford Motor Company

 

[J.Rovirosa]

Bringing this back up because I think I might have fixed it, or at the very least eliminated some of the shifting weirdness the truck's had for awhile.

First off, thanks for the tsb info, swetrid. Replacing the pcm will be the next thing I do if this isn't the fix.

Basically, I think the tps went bad. Replaced it with a Motorcraft part that corresponds to the current, non-updated pcm calibration and the shift quality is much improved and more consistent. No longer bangs into reverse from park, and no longer has the downshift coast clunk it's had since I can remember. It's still too early to tell if it will throw the code, but I'm thinking these shifting issues contributed to it.

 

[explorer95357]

Bringing this back up because I think I might have fixed it, or at the very least eliminated some of the shifting weirdness the truck's had for awhile.

First off, thanks for the tsb info, swetrid. Replacing the pcm will be the next thing I do if this isn't the fix.

Basically, I think the tps went bad. Replaced it with a Motorcraft part that corresponds to the current, non-updated pcm calibration and the shift quality is much improved and more consistent. No longer bangs into reverse from park, and no longer has the downshift coast clunk it's had since I can remember. It's still too early to tell if it will throw the code, but I'm thinking these shifting issues contributed to it.

When you mention tps do you mean throttle position sensor? Also why did you replace it? Did you have a check engine light on? I dont have my check engine light on but I have a 646 code on my 95 explorer which is a 2nd gear problem. Search my posts for overview of my situation and hopefully you can provide some insight. TThanks in advance

 

[J.Rovirosa]

Yeah, the throttle position sensor. And I regret to say it didn't fix the problem. Once the drive cycle is completed, it will eventually start throwing the code again. Going to try the recalibrated pcm next.

 

[explorer95357]

Yeah, the throttle position sensor. And I regret to say it didn't fix the problem. Once the drive cycle is completed, it will eventually start throwing the code again. Going to try the recalibrated pcm next.

So you still have the trans code? Ive tye 646 and I was kind of hoping that I would be able to try and repair myself since its pretty specific 646 code. I see that the code could be for a number of things though. Valve body gasket. Bands broken. Filter etc. But apart from the bands I can do the above mentioned. Its just been so cold here in chicago and Ive had no time to get to it. I will eventually post results and let you know what was done and what the results were. Thanks