I just got my 98 ranger running with the sohc motor, harness, & computer from 2002 explorer 4.0 sohc. Now im getting a p0791 code, my overdrive light flashing & weird shifts. I have been reading online & i saw smthen that said the 02 explorer transmissions had the intermediate shaft speed sensor but i dont think the trans in my ranger does? Also the donor explorer is a 2wd & my ranger is 4wd. Is there a way i can trick the computer into thinking i have the iss or is there a way to add it to my 4wd ranger trans? Or maybe some sort of computer tune to eliminate the iss? Not that i have anyway of doen that or would i even know where to start looking for someplace to do that kind of tuning. Or should i just live with it? Thanks to anyone that can help!

 

P0791 Intermediate Shaft Speed Sensor Circuit
Circuit is the key word here

The ISS was never used in the computer strategies as far as I know, but its wires are still there and connected to computer

Your 1998 5R55E trans should have had the ISS sensor, drivers side up by bellhousing, picture here: http://www.atraonline.com/gears/1999...gmar99p49a.jpg
It was eliminated in 1999 5R55E models but you could have a later model 1998 so sensor was removed.

Fix from Ford was to cut the 2 wires for this sensor and strip the ends then twist them together, that will give the computer a complete circuit for that sensor so no P0791 code any more
Computer looks for disconnected wires and sets that code

 

Are u serious! Thats it? You are amazing thank u very much! I just put the ohv computer back in thinking that would help it shift better but it didnt & at the moment im stuck on the side of the rd & it died & isnt wanting to re-start luckily im not far from home but as soon as i get this thing home ill twist those wires together & let ya know how it goes thanks again!

 

Article that it comes from is here: gmar99p49

Read paragraphs just below picture

I read this in a Ford TSB as well but couldn't find it

 

Pretty interesting? So do u think i have a diff issue then because i did cut the plug off & twist the wires together & im still getting the p0791 code? Whats weird tho is the explorer is an 02 & either u or that article says they eliminated that sensor in 99? If so then i wonder what the extra plug i just cut off & twisted together was for & if they didnt put the programming in the computer for it how could i get the code still? Do u think maybe they started to use that sensor in the 02 explorer? Also i read smthen online about using the computer out of a 97 explorer sohc 4.0 for the ohv to sohc swap i thought mainly for getting around the pats issue but do u think i could use the 97 explorer sohc computer to run this 02 explorer sohc? I ordered one off ebay for 25 bucks figured if it works awesome if not its only 25 bucks. Just so u know the truck is running great but its shifting weird especially from 2nd to 3rd wich i read something about that being kinda common i think they called it like a 2nd to 3rd flare or smthen also my speedo after about 40mph just kinda bounces back & forth from maybe 30-40 to 60-70ish & my overdrive light flashes & of course the p0791 code. But if i run my ohv computer i dont have the weird 2nd to third flare thing well it like revs up a lil in-between the shift & then shifts kinda hard into 3rd it doesnt do that although it doesnt seem to shift as smoothly thru the rest of the gears as the sohc computer does & it also will make my overdrive light flash & it will throw a p0500 code for the vss wich i pulled the one from the explorer just to see if the ranger one was actually bad wich it wasnt i dont think since my speedo still worked oh also with the ohv computer my speedo works as it should? Thanks again for all the help rond i think i might have gave up by now if it wasnt for your amazing help!

 

I forgot about the speedometer, and that may be the problem, certainly the shifting part and speedometer

In 1998 to 2000 Rangers the rear ABS sensor(VSS) was used for the speed signal, it ran to the GEM, behind radio, where the GEM converted the 20,000PPM signal to the 8,000PPM signal the speedometer, cruise and the COMPUTER used

In the 2002 Explorer(or Ranger) the speed signal came from the OSS(output shaft speed) sensor, it was on the transmissions tail shaft (or transfer case)
OSS sensor connected directly to the 2002 computer, and the COMPUTER converted the signal to 8,000PPM and sent it out to the speedometer

And there in lies the problem

Are you using the 1998 transmission wiring or the 2002 wiring , they are different?

 

Im using the 02 trans wiring because the sohc harness from explorer didnt have a separate plug for the trans wiring like the original ranger harness had what about a diff yr computer? Or do u know of any way or anyone that can tune my computer to work with what i have?

 

2002 harness is good

On the 2002 trans harness you should have had the one larger 16 pin connector and TWO separate 2 wire connectors at the transmission

The one with Grey/red and grey/orange wires is for the ISS sensor and the one that would be cut and twisted together, but I find it odd this wasn't already cut and twisted on the 2002 harness

The one with grey/red and dark blue/yellow is for the OSS sensor(speed) which would be on the tail shaft housing of a 2001 and up 5R55E transmission, but not on the 1998 5R55E<<<is this the one you cut????
This is the one that causing the issue with transmission shifting, its missing

Look on the PCM connector pin 68 there should be a Grey/black stripe wire, that's the Speed signal OUT to the speedometer, and cruise, which doesn't work because there is no speed IN from OSS sensor
In a 1998 that connection would interfere with the GEM modules speed signal out

Good read here on what is happening: https://img1.wsimg.com/blobby/go/197...aet_808115.pdf

The 5R55E uses a 12 tooth OSS reluctor wheel, picture here: https://www.picclickimg.com/d/l400/p...uctor-Type.jpg
So computer gets 12 pulses for 1 rotation if output shaft

The only speed sensor you have access to is the rear axle VSS and its reluctor wheel, which has significantly more that 12 teeth, lol, seen here: https://i.ytimg.com/vi/8iirGahHbCw/maxresdefault.jpg
But it also turns at 1/4 the RPMs as output shaft, i..e 3.73 or 4.10 axle ratios
If rear axle had 48 teeth then it would be close, but it looks like is has about 84, haven't counted it

So you need a way to convert the VSS signal down to OSS pulse count

Dakota Digital has the SGI-5E, which does this type of conversion, but I am not sure of the settings to use, seen here: Universal Speedometer Signal Interface

This would be spliced into the rear axle VSS wires, then connected to the dark blue/yellow wire on the PCM pin 84
You would lower the pulse count from the VSS to mimic the pulse count from OSS so PCM would have correct speed so it can shift gears accordingly

You can access VSS sensor wires at GEM module behind the radio, but would need a wire to engine bay to connect to pin 84 wire
There is a Grey/red wire on PCM pin 91, it is the signal reference this may also need to be connected to the Interface but I would first just use a local ground as the 1998 wiring grounds the VSS to just use 1/2 the signal like OSS does with the grey/red wire

1998 GEM wiring below
Pin 9 is the IN from VSS
Oin 1 is the VSS OUT to speedometer and computer(this computer wire is what interfering with speedometer I think)

 

so your saying i need to order one of those dakota digital signal converter things & then wire it up like that? Or are u saying to try to wire it up like that first?

 

I just checked & i definitely cut the one with the gray/red & gray/orange wires but it looks like the plugs are the same should i maybe try to wire it back up & plug that one in instead?

 

gray/red & gray/orange should be the ISS sensor wires, and you don't have an ISS sensor right?
Drivers side by bellhousing up at the top?

There should also be a grey.red & dark blue/yellow set of wires, did you find that connector?
That the the OSS sensor wiring

And yes, I think you will need the SGI-5E to hook up the rear ABS sensor to the PCM so it has a speed signal, which it doesn't now, that or swap in a 2001 or up 5R55E, lol
This is a 2WD right?

ISS and OSS sensors at the bottom of diagram, wire colors should be the same for explorer but not sure

 

My trans does not have the iss sensor. & yes the oss sensor i found & it is/was hooked up. So im guessing that the pcm from the 97 explorer sohc isnt gonna help my problem? Im assuming if it was that easy u would have already told me to go that route? I already ordered one but it was only 25 bucks so if it wont work its not a problem. Do u think it might work better then the 02 pcm to use with the signal converter thing tho? Also would the 97 explorer pcm i ordered need to be flashed or programmed to work with my ranger? I also just wanted to tell u that i really appreciate u taking the time to help me with this! Idk if its aloud on this forum or not but id like to send ya a couple bucks thru maybe paypal or smthen you have saved me alot of time & money & i would like to be able to give you something for your time?

 

I am confused, 5R55E transmission didn't have an OSS sensor until 2001??

Does your 1998 5R55E have one?

If so then I am way off here.

 

Idk i cant find any pics that have the same sensors as mine online. Mine has the one rear oss sensor? I think thats what it is anyway? Its at the rear of the trans kinda on the top. But it doesnt have any other speed sensors that i can find? My vin tag on my door has a D for the trans code wich i read means its a 5r55e?

 

I believe this is the oss sensor?

& i think this is where the iss sensor would be if it had one?

 

Yes, that is the OSS sensor

And yes thats where the ISS would be
That sensor was called OD drum sensor, Coast drum sensor, and ISS sensor, but never used on any 5R55E

If you have the OSS sensor hooked up then trans should shift fine, so puzzling

More info here on sensor placement: Untitled Document

The PCM's speed output signal used on 2001 and up Rangers may be interfering with GEM speed signal causing the issue with speedometer
Have a look at pin 68 on the PCMs connector, should be a grey/black wire, that is the VSS signal OUT to vehicle, used in 2001 and up, goes to speedo and cruise, disconnect it
GEM will provide speed signal for speedo and cruise as it did before the swap


Picture in post 10 of this thread shows a different sensor above shifter, never seen that one before??: https://www.explorerforum.com/forums...n-mine.357691/

This thread deals with different year swaps so good read

 

ok so i cut the gray/black wire & my speedo is working like it should but still have the weird shift from 2nd to 3rd & my overdrive light still flashing with p0791 code i actually tryed switching the plug & i plugged the iss sensor plug into the oss sensor & i get an oss sensor code? Any chance it would help if i wired them together then plugged it in? Seems like when i plugged the iss sensor plug into the oss sensor it was using the oss sensor for the iss signal? So if i were to plug them both in maybe somehow that could work? Also i got the 97 explorer pcm today & tryed that & it actually helped (no flashing od light & speedo worked) but it had a slightly weird shift when first taking off from a stop & didnt seem to have the power it should have also didnt want to downshift very well?

 

So ive eliminated 2 of the three trans issues i had although of course the main one the 2nd to 3rd shift flare ive seen it called i still have but i guess ill just live with it for now? I ended up wiring both the iss sensor & oss sensors together both sensors have a gray/red wire & another wire i wired the 2 gray/red wires together & the other 2 together (had already cut the iss sensor plug off so i wired those wires to the oss sensor plug & then plugged the oss sensor back in) & its no longer throwing a p0791 code & with ron.d's advice i cut the gray/black wire (pin 68) & my speedo is working although its off a lil i think that is because i have slightly bigger wheels and tires. So idk ron what do u think? Would getting one of those speedometer signal converter things be any better than what i have now? It would be nice to get rid of the weird 2nd to 3rd shift? Im pretty sure that its caused by the diff trans speed sensors since if i run the 97 explorer sohc pcm it doesnt do the shift (flare) thing although it does some other strange shift things? I may try one more time to run that pcm with the 2 sensors wired together & see if that makes any difference

 

No, I wouldn't hook the ISS wires to OSS wires and to OSS sensor

I get it that the P0791 code goes away but that just a "heads up" code, shouldn't cause the shifting issues

Grey/red wire in on pretty much every sensor in the engine and trans, it the ground reference.

No you don't need the SGI-5E, I thought you didn't have an OSS on the 1998 5R55E, you do so no need for that


Here is the problem I think you are having, and I had, there were TWO different "ISS", input shaft speed sensor(the one by the bell housing), and the intermediate shaft speed sensor (one above shift linkage)

The 5R55E didn't ever use the input shaft speed sensor so those wires could be twisted together
Later years DID use the intermediate shaft speed sensor

Intermediate shaft speed sensor is above shifter, drawing here in post #4: https://www.explorerforum.com/forums...achine.404125/
it is above the shifter
So twisting the wires together won't help, won't hurt either, lol

The 1997 PCM may want a VSS speed signal from the GEM module which is why it has different shift issues

Outside of swapping out the 1998 5R55E to one with an intermediate shaft speed sensor not sure how to fix this

 

Update

The 1997 5R55E PCM may work

PCM Pin 58 is the VSS IN from GEM module, also a Grey/black wire like on pin 68 which was the speed OUT on the 2002 PCM

Since cutting that made speedo work again, I "assume" that grey/black wire IS connected to the GEM wiring already so............connect it to pin 58 on PCM

And twist ISS wires together, thats pin 59, it was OD, Coast clutch, or Input shaft sensor hook up in 1997-2000 PCMs

 

So i hook pin 68 to pin 58? Or pin 59? Cuz my wiring is missing pin 58?

 

I cannot find a pcm pinout for the 2002 explorer pcm wiring anywhere! & on my pcm plug pin 58 is empty?

 

The grey/black wire in the harness, that was on pin 68, needs to go to pin 58, so no you don't hook pins 58 and 68 together
You hook the wire that was in 68 into 58

The wiring harness is 2002 so it won't have a wire on pin 58 because that is Speed IN
In 2002 the PCM used the OSS to calculate speed then sends that OUT to speedometer on pin 68

The 1997 PCM has OSS but just uses it for Ratio calculations, not speed, so there is no speed out on pin 68, 1997-2000

So it needs a Speed signal, on pin 58

In 1998-2000 that speed signal comes from the GEM module
And from the reaction of the speedometer with 2002 PCM pin 68 hooked up I assumed that grey/black wire has GEM connection via speedometer, so interfered with speedometer.

Short video here on repinning Ford Connector:

You could pull out the 68 pin and wire and use it in 58
Wire colors would also match

 

Man you sure know your stuff idk what id do without all your help thanks again! Ive been out in the garage for hrs now trying to find another gray/black wire for the vss to connect to pin 68 i never even considered actually putting a new pin in to 58 your a genius! Im gonna do that rite now!

 

This is new territory for me, and I am hoping it works