Yesterday I posted on here that my speedo had died. I also stated that I was able to pull a DTC of P0500 and that my tranny was acting wierd and my ABS light had come on. All of this led me to believe that my VSS was bad and needed to be replaced. So off to the dealership I went and I purchased a new VSS. Thanks again Chris and Robin for the responses on how to change it. (FYI for anyone else in the same boat, the bolt you need to remove is a 10mm) After I had the new VSS installed everything worked fine. I was having battery issues at the time so I was not able to clear the DTC. About 2 hours later, I start up my truck, put it in gear and drive to my dad's house. I looked down and the speedo was not working again. Could this be because the truck was at about 25% of operating temp when I drove away? Thats was the only thing I could think of at the time. Then I remembered that I still needed to clear the DTC, which I did. When I started it back up, everything was running fine again. The only other thing was that when it was not working the overdrive on/off light on the column shifter was flashing and when it was working fine it was not flashing. Does anyone know what is goin on with my truck? Should it be OK now that I cleared the DTC? Could the flashing overdrive switch have something to do with the problem? If so what? I also checked the A/T fluid today. At normal operating temp it seemed as if it was too full. I thought this was wierd since I have never added any so I double checked and the entire whit part of the dipstick was covered in fluid. Does anyone have any suggestions or should I just wait it out to see if it happens again? Thanks.

 

I do know that a bad VSS can make the O/D light blink. I don't know if the PCM just starts ignoring the VSS signal if it receives a bad communication or detects a failure which would explain why it may not have worked.

I've helped one member here with a VSS issue, but I cleared the code before it was changed. The manual only lists a bad VSS or some wiring issue for that code, so I'd say keep your receipt in the glove box in case you need to change it again. Wouldn't be the first time a new part ended up being bad. Until then, I'd take a couple of test trips with it and see if it acts up again. If not, I'd ignore it.

Hopefully someone else knows how this works for sure.

 

maybe the VSS code may be for the other VSS on the transmission which is more likely to affect the speedo
I think I remember they are both the same part# so you may swap out the sensor you removed with it

 

The VSS does control the speedo Ray. The 2 sensors in the tranny are the OSS & TSS (output shaft speed and turbine shaft speed) which measure incoming and outgoing RPM's in the tranny. Since the rpm's will change with each gear, they're not a good place to pull the speedo reading from. (now you've got me thinking back to the old trannys and where that plastic speedo gear hooked into. had to have been something on the output shaft, but how did it compensate for gear changes? been too long )

Anyway, the sensors in the tranny have their own set of codes.
P0500 Vehicle Speed Sensor (VSS) Malfunction <o></o>
P0503 Vehicle Speed Sensor Noisy<o></o>
P0715 TSS Sensor Circuit Malfunction Fault<o></o>
P0717 TSS Intermittent Failure<o></o>
P0718 Noisy TSS
P0720<st1> <st1:city w:st="on">OSS</st1:city></st1> Sensor Circuit Malfunction<o></o>
P0721 Noisy <st1><st1:city w:st="on">OSS</st1:city></st1><o></o>
P0722 <st1:city w:st="on"><st1>OSS</st1> </st1:city>Intermittent Failure <o></o>

 

When my VSS went out I had a constant ABS light, flashing OD light and no speedo. New VSS cured it all. That was at least 4 years ago and no problems since. The VSS is also an integral part of the ABS. Some parts shops have it listed as an ABS sensor. The PCM flashes the OD light when it detects certain tranny problems. Maybe if the VSS is bad the PCM thinks there is a tranny problem because it is monitoring the OSS and is looking for a correlation between the two. JMHO

 

I guess different truck behave differently
when mine went out ABS light on brake malfuntions no speedo problems
I pulled the sensor to check for shavings or whatever,put it back in without replacing wire drove to dealer to get new one still no speedo problems same as before

 

Maybe mine being an Early Bird makes the difference. Older PCM, much older, 3-98.

 

I have the same problem with od flashing and causing because the fuel tank been clog and no enough fuel going thru injector i don't but chris halp me find the problem.Dealer mechanic just clean speed sensor sometimes bad reading causing pieces metal on sensor. Thank you Adam

 

I was thinking metal on the sensor as well. Mine was bad awhile back and I ended up doing a ful fluid change in the rear just to be sure everything was clean.