speed sensor question...
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Joined: Jul 2004
Posts: 5,946
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From: in the woods of MA
speed sensor question...
I have a '97 F-250HD with an automatic that occasionally loses it's mind. When attempting to accelerate from low speeds, 10-25 mph, it will sometimes go into what appears to be neutral, then eventually drop hard into low gear and the next shift will be real hard. Sometimes it logs errors (flashing OD light), sometimes it doesn't. Very intermittent, will do it a lot, then won't do it for months. I had it into a tranny shop and it did it for them once, so they believe that it's not just me, but they couldn't find anything wrong. According to them, the codes it logs are Speed Sensor errors (I don't know the exact codes). They claim that if that was really the cause I would see weirdness in the speedometer behavior, so it's probably not the speed sensor but that the signal is going bogus somewhere between the sensor and the tranny. Seems that that signal goes through multiple units before getting to the tranny, like the ABS (which I've never had any problems with)
So my question to you folks is: If you've had a verified case of a bad speed sensor, did you see erratic or otherwise bad behavior in the speedometer? My inclination is to just replace the sensor (they can't be that expensive, right?) and see if the problem goes away.
Oh, one more question - I don’t' have a code reader, that's on my wish list. Are the transmission codes read out through the same interface as the engine codes? Same reader?
TIA,
- jf
So my question to you folks is: If you've had a verified case of a bad speed sensor, did you see erratic or otherwise bad behavior in the speedometer? My inclination is to just replace the sensor (they can't be that expensive, right?) and see if the problem goes away.
Oh, one more question - I don’t' have a code reader, that's on my wish list. Are the transmission codes read out through the same interface as the engine codes? Same reader?
TIA,
- jf
Senior User
Joined: Jul 2002
Posts: 123
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From: Mt. Airy, MD
I think you only have the rear abs for your year, might try checking the RABS. Not sure if yours is on top of the transmission or rear wheel. Vehicles equipped with rear anti-lock brakes (RABS) generate a vehicle speed signal from the rear axle speed sensor. This pretty much controls everything thats vss controlled and may be your problem. A code reader is going to pick up every code that is set by the vss failure. Should pick up transmission codes that are also causing problems.
