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p0500 but speedometer works fine and no abs light


integrx18

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ford
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hi im new to this site but I have done a weeks worth of reading and now have finally broken down and joined because I cannot for the life of me figure this out. I bought a used gem module that was an exact match for my truck (exact numbers on the case) This made me wipers, domelight, and 4wd all worked again. the speedometer originally didn't work when I got the truck and all testing led me to think it had to do with gem module due to all other faulty systems. Well the speedometer still didn't work. after some more electrical testing I found a bad ground to the vss sensor in the transfer case. I ran a direct ground wire to the sensor and wala the speedometer worked again. I drove the truck for a few miles and the check light came on p0500 vechicle speed sensor a. from my belief of reading about this I assume that this would eliminate the rear abs speed sensor in the rear diff. But I replaced the rear sensor anyways after ohming the original sensor and knowing it was good. Now I tested the black grey wire going into the pcm and it also gets the voltage ac that it requires. I don't know why im still getting p0500 my speedo works and pcm gets the signal....... any ideas.... maybe something else could cause this ? Im lost and frustrated. I just want to get rid of the code because nobody will buy the truck with the light on. I also don't have any abs lights on. please help
 


integrx18

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ford
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update.... I just doubled checked everything that I can think of. just realized that the ecu does not get a signal from the vss. the black grey wire gets signal to speedo and gem module but never gets to the ecu. so I ran a direct jumper wire from sensor end of black grey wire to the ecu so that should give it the signal.....unfortunately still no speed reading on scan tool. this doesn't make sense unless the gem module changes the ac voltage reading to some other reading and then to the ecu but from the vss wiring diagram I have it looks like the black grey wire just goes to the speedo , ecu, and gem module as if one wire breaks off into three to get to those places? im lost im starting to think that the gem module sends the ecu some speed reading but cant find anything on this. I cant get this vehicle to pass emissions with the p0500 code showing up...uggggggghhhh
 

RonD

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Here is a 1997 VSS wiring diagram: http://ww2.justanswer.com/uploads/FO/fordguy4u/2013-05-22_172049_a1.jpg

The PCM(computer) is connected independently, as are Cruise(amplifier), GEM and speedometer, to the VSS.
There is no speed wire between GEM and computer in 1997

The PCM(ECU) is generating the P0500 code.
And since speedometer is working the you know the VSS is working, so one of the wires to the PCM is not working.
Splice S111 or Splice S110 could be at fault or the wires at the PCM could be

The location of these splices is only found in an EVTM book for 1997 Ranger, this is a technical manual that shows wiring and locations.
They are specific to model and year, so an 1996 or 1998 might help but might not.

Since you know the Location of the VSS, on the transmission/transfer case
And you know the location of the PCM(computer) and the pin numbers used for the VSS wires on that connector, look at wiring diagram for pin numbers.

I would use an OHM meter and long jumper wires to see which wire, the Grey or Pink, has lost its connection between VSS and PCM.

Then you can either trace that one wire OR....................run a new wire, spliced into VSS wire and PCM wire

1996 PCM/ECU location: http://www.ford-trucks.com/forums/attachment.php?attachmentid=363&stc=1&d=1052748771

1997 should be the same, disconnect battery before removing connector.

PCM/ECU pin numbering here: http://www.ranger-forums.com/attachments/4-0l-ohv-sohc-v6-tech-33/62644d1377656726-anyone-have-97-4-0l-ohv-pcm-pinout-97-explorer-pcm.png

Pin 33(pink wire) and pin 58(grey wire) are the ones connected to VSS

It could be the Pink wire is the issue, and it is a Ground wire so in theory you could just Ground Pin 33 to test if that is the problem

And you could find some corrosion in that PCM connector, and that may be the problem, that firewall location did have a water intrusion issue if hood gasket leaked above it, in later years Ford added a cover for it
 
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