I have a 1994 ranger that was previously a 2.3l, swapped with a 4.0 sohc and 5r55e. Some info from the swap: motor and trans were sent to my uncle in 2000 during his Offroad race career with Ford. He put a season of racing on the setup before it was pulled and stored until 2 years ago when he swapped it in this 1994 ranger. He performed the swap without any problems and drove the truck off and on for about a year until I bought it from him. I did some suspension work over the course of a year and just recently “finished” it. I drove the truck for about a week when all hell broke loose. The transmission started shifting funny, wouldn’t downshift when I came to a stop, wouldn’t go into overdrive, holds gears until I let off the throttle, etc. I got my hands on a scan tool and found out it throws code p0500 BUT only when the vehicle comes to temp. This part is critical because to this day it shifts fine, great in fact UNTIL it heats up... P0500 Is a code for “vehicle speed sensor circuit malfunction.” Only thing is I don’t have a vss and my uncle assured me he never ran one in his race truck, and that the trans gets its shift scheduling from the OSS (output shaft speed sensor). I’ve gone over the schematics for the vss and the circuit multiple times to see if there could be something I’m missing and it appears I don’t even have a wire for it going to my ecu (it goes to pin 58 which is not pinned). Id like to think I’ve narrowed it down to 2 possibilities, the first being the ecu. I have a computer out of a 97 explorer (code: ttb4), could that be looking for the trans shift signal from the vss where a newer computer from say 2000 (code: cde4) would get it from the oss...? The other possibility I’m considering is damage in the harness. What would be the most straight forward way to test for shorts or weak signals between sensors and the ecu? Take the whole harness out and look for tears? Ohm out each terminal? Shops won’t touch it because of the swap so access to a good scan tool is kind of out of the picture... any help would be greatly appreciated, I’ve been chasing my tail for about a month now with no results...

 

Welcome to the forum

Yes, the 4.0l SOHC with 5R55E trans used an OSS sensor on the rear of trans but not as a "speed" sensor it was a ratio sensor for trans shifting its wires run directly to the PCM(computer)

In 2001 and up the OSS signal was used as a speed signal, the 2001 and up computer got the OSS signal as usual and then converted it to 8,000ppm to send out to speedometer and cruise, as needed

Yours 1997 or 2000 computer still expects a VSS signal as well as the OSS signal, should be a grey/black wire on pin 58 of the PCM(computer)

1994 Rangers had a VSS but it was on the speedometer cable so long gone, lol

I assume you have a speedometer, does it work and what year cluster is it, 1995 and up had the electric speedometers
If its working then you have a VSS, it could be on the rear axle, ABS sensor, and runs to a GEM Module that converts it to the 8,000ppm signal the speedometer and PCM expect to see
And yes that signal wire to the PCM could be failing, corroded connector can be effected by temp changes

So find out what year the cluster(speedometer) is and where the GEM or speed conversion module is for the VSS, i.e. what makes speedometer work, lol

 

Thanks for the reply. The dash is 1994, the speedo does not work because I have a 9” axle and the old vss cable/sensor removed... do you know if it’s possible to flash a 1997 ecu to get its speed signal for the transmission from the oss? I don’t have any desire to make the speedo work, just need transmission function back...

 

Something else I just noticed is my harness must be from a 2001 based on some wiring charts I have because that’s the year they did not incorporate a pin 58 (vss)

 

 

So you have a problem with the 1997 or 2000 computers, not sure about deleting the need for the speed signal on those years, could try later model computer because it sends OUT the speed signal, so doesn't need an external one coming in

Oh wait, you can use an SGI-5E with the OSS to send in a recalibrated VSS 8,000ppm signal to pin 58

Seen here: http://www.dakotadigital.com/pdf/SGI-5e.pdf

Not cheap, $85

And not sure how you would calibrate it without an electric speedometer hooked up


OSS and VSS sensors are exactly the same type of sensor, just FYI, Ford changed the name for the transmission sensor because there where TWO at that time, a VSS and an OSS
So the OSS sensor signal which is probably 30,000ppm can be re-calibrated to the 8,000ppm the PCM or speedometer expects

 

Oops, you can't switch to a 2001 computer, you run it to a problem with the transmission, the 2001 5R55E got an added ISS(intermediate shaft speed) sensor, and 2001 computer will expect to see that signal
Its an external sensor added just above shifter on drivers side, have a look, you may have that sensor if transmission is a later model, the 2000 and earlier PCMs just wouldn't care because they didn't need/use it, 2001 and up PCMs need it

 

Thanks! I’ll talk to my ecu guy about an 01 ecu, only problem with that would be the pats system which would have to be flashed out... either way I’m probably looking at around 85 for an ecu or the Dakota digital digital interface. If I were to get the Dakota digital thing and a speedometer, would I just run a second wire from the oss output, through the Dakota digital, through a speedo, then to pin 58...?

 

I do have an iss but no wires going to it...

 

Read about the 2001 PCM in last post!!!

Yes, but not "though the speedometer"

The OSS, like a VSS, has one wire as a Ground, it generates an AC voltage signal, its not powered, it makes its own AC Voltage, which is a Sine Wave, only the Positive half of the wave is used

The AC voltage itself is not used, just the wave, the faster the waves the higher the speed, that's the PPM, pulse per mile

So you just need to tap into one of the OSS wires, dark blue wire on the 1997 diagram at pin 6 on PCM
run that tap to the SGI-5E input
Then ground the sensor input ground wire, that should ground it to the PCMs reference ground

The output is run to speedometer and PCM separately just spliced wires, the speedometer needs to be grounded, PCM already is so it just needs the 8,000ppm output of the SGI-5E

 

I guess I was thinking that since I have an iss that isn’t hooked up, I could run a plug to it and use an 01 ecu successfully... sounds like I’ll be going the Dakota digital route though. One last question before I order it, since I’m converting the 30,000ppm** to 8,000 would I just look for an 8,000ppm speedo from jegs or similar parts source...?

 

So you do have a 2001 or newer 5R55E then that's OK

About the speedo yes, a Ford replacement speedo, Ford always used 8,000ppm, still does

 

Awesome thank you for all the help! We’ll see if it works mid next week when I receive my Dakota digital sgi-5e and universal jegs speedo... as for the grounding of the oss, would you mind elaborating on that..? The dB/y is the signal wire so just ground the Greg/red...?

 

Yes, the OSS should have 2 wires
Dark blue/yellow is +
Grey/red is -

You can splice into both of those wires and hook them to SGI-5E just to make it simpler to do, both wires are at the PCM, + is 84, - is 91

91 is the reference ground of the PCM, they use this for sensors because local grounds, at the engine or frame, may not always be "good grounds" lol, ground straps corrode and get left off.
But assuming the best you just need to ground the speedometer and then run the SGI-5E 8,000ppm wire to it and to the PCM pin 58

This is assuming using the 1997 or 2000 PCM, you don't need this for a 2001 PCM it didn't need a VSS signal, it outputted the 8,000ppm signal to the speedo and cruise

Is outputted even a word, lol

 

Thanks! Minor plot twist, DB/Y goes to pin 6 and pin 84 is DG/W... also with the ecu plug in front of me it appears pin 58 is in fact pinned with a GY/B wire that is cut after the engine to vehicle connector... so my question is do I splice into the dB/y wire or dg/w? With the discovery of an intact pin 58, and by the looks of my wiring chart, I’m assuming my harness is year 2000 not 2001 thus making pin 6 oss and pin 84 tss...

 

You would need to go with the year of the PCM

So which year PCM are you using?

If 2001 you don't need VSS signal in, OSS is on 84/91
Then VSS output is on pin 68, for speedo, cruise, gem

If 1997/2000 then wiring should be correct
OSS 6/91
VSS in 58

 

Copy that. I’ll update when I get my speedo and sgi-5e and hook it all up

 

Got my parts in early and just finished wiring and calibrating everything aaannnnddddd trans still shifts like **** and I still get my vss code “p0500” on the bright side I now have a working, accurate speedo... not too sure where to go from here though... probably pull my wiring harness out tomorrow night, lay it out, cut it open and inspect each and every single wire for splits and what not...

 

Good that you got it working and a speedo signal

VSS signal IN, "+", at pin 58, I would test if that wire has continuity to SGI-5E OUT connector

Pin 33 is the "Case Ground" for the PCM and also where the "-" VSS signal would be connected, test continuity between 33 and signal "-" on SGI-5E
Case ground wire may not even be connected/grounded, so no "-" signal at PCM for VSS "+" signal so P0500

 

I’m fairly certain all the wiring is correct but It never hurts to triple check, I’ll do that when I get home today and report back

 

2001 wiring harness won't have a connection to pin 33......................................so for earlier PCM use you will need to add a Ground wire there and that should take care of the Speed signal ground as well, or also ground speed signal "-" to same ground point as pin 33

 

Case ground is 25 on my chart and on my ecu connector. 33 is not used... I connected the vss return signal to pin 91 “signal return”

 

Is your wiring diagram for the Year of the PCM?

1997 I thought

What year is the PCM you are using?

 

PCM:1997
motor/trans/harness:2000

pulled my intake manifold off a couple hours ago and found a huge rats nest. At least 4 handfuls of insulation later I found some chewed wires.

my wiring chart says this is “hego htr 11” pin 93, red/white. And the black/white is ground, pin 24 I believe. My other wiring diagram indicated this is o2 sensor #1 and I don’t believe it was ever hooked up but I’m doing some digging on that right now. Either way, this short COULD potentially be responsible for ecu malfunction... right..?

 

O2 sensors are 4 wire

I don't see red/white and black/white sharing a connector in the engine diagram

I see the red/white at pin 93 and that it does go to O2 sensor but no black/white wire with it on that 4 wire connector

Yes black/white was often a ground wire, but O2s used computer pin as ground, and no black/white wires

Just below your hand in the picture is a 2 wire plug-in, what is that?