So im having an issue with my speedometer, first im a 99 f150 v6 4,2l standard 2wd lowered down truck , the speedometer stopped working and my odometer, i put scanner on and said code speed sensor or the differential, now i have changed that , ran the codes and nothing abs light is gone , but speedometer is still not working or the odometer, now im stumped i have went through numerous threads and everything pointed to that vss sensor even the scanner ...so now im at a loss....what could be happening maybe the psom module or the cold solder that everyone says thats on the dash circuit board if so how to i test the psom module any help would be greatly appreciate..James



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The VSS resistance should be between 200-300 ohms.

Check if the scanner can detect the vechile speed or Check if Cruise Control is working. If the PCM can detect the vehicle speed remove the instrument cluster and check the wiring.

 

so i now took the vehicle for a ride and the code p-o720 saying the speed senor again, though ive just put a new one in it , so where does this signal go from the vss sensor directly to the pcm then to the psom module behind the dash?could the wire be b ad somewhere from the sensor to the dash
??? oh ay and the cruise control doesnt work again this is a 5 speed manual

 

I had 98 crown Vic and lost the speedo and odometer and it was a blown fuse. Not sure how these trucks are setup but could it be that maybe? Might be a stupid question but just a thought.

 

actually i have checked all the fuses in the engine bay and under the dash all of them are fine took everyone out and inspected them visually, so its not that ..i know there is a short in the circuit somewhere between the vss sensor and the psom module that runs the speedometer and odometer but i cant find any info on where to check and how...ive replaced the vss sesor and nothing code still pops up po270 so i am at a loss..i have visually inspected the connector at the vss sensor seems fine looked at the wiring going under the truck till it goes into the main wiring cant see anything ..so what i have found and read it could be wiring at the pcm or the psom inside the dash cluster tommorow going to take out the cluster and nlook for that cold solder joint that apparently is a common problem...if thats not it im stumped...anyone with any expertise or has had this problem and found out what it is could you please help...really dont want to take it to ford and have them soak me for hours of diagnosting time...thank you

 

Which speed sensor are you checking / replacing? If I remember right there is one in the rear diff, and one on the trans. If the rear diff one is bad, the code would be p0500 or somewhere in there. If it's the transmission speed sensor (output shaft speed sensor) it'd be more like p0720, p0721, p0722....

 

thats makes sense know i was confused as to what sensor did what and what codes did what...so i have replaced the one on the differential and just waiting for the shop to get the other one in on the tranny and hopefully this solves my problem...thank you james

 

so i changed the oss sensor now inspected the wires there all fine and still the speedometer or odometer doesnt work , which is startingto lead me to believe the problem is the cluster the bad cold solder joint or the psom itself? any thoughts how do i test this any help always appreciated...

 

The cold solder joint only effects the light in the odometer. At least on my 99 anyway. I would look for the wiring harness touching the exhaust some where first.

 

so i checked the wires underneath the truck from the vss sensor and the oss sensor they all look fine no fraying nothing this truck was kept immaculate , so what now, still throws p0720 code how do i test the signal from the oss sensor to the pcm ...