RABS Sensor
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RABS Sensor
Driving home yesterday and my speedometer hangs up and the mileage meter disappears plus the truck starts shifting hard, 95 f-150 extended cab 5.8 engine. Fearing the worst, tranny problem, I call my transmission guru explain the situation to him he says check the rabs sensor plug on the top od the rear end. OK I find the sensor and pull the plug connector the sensor connector is wet as in full of oil. I pull the sensor out of the rear end mostly out of curiosity and notice the female plug end has oil in it too. I grab some alcohol and clean both the plug and the sensor and while I have it out take an ohm reading on the sensor pending on the scale it reads 1.5 or 150 or 1500 ohms plus or minus 20 or so.
I stick it back in plug in the plug and start the truck the mileage meter lights up mometarily then blanks out and its still out truck still shifts hard and no speedo sits at zero when in motion. I ordered a new sensor but am curious as to what else may be wrong due to the fact that my wiring diagram show the circuit going into the engine computer and then no indication what happens after that.
Scott
I stick it back in plug in the plug and start the truck the mileage meter lights up mometarily then blanks out and its still out truck still shifts hard and no speedo sits at zero when in motion. I ordered a new sensor but am curious as to what else may be wrong due to the fact that my wiring diagram show the circuit going into the engine computer and then no indication what happens after that.
Scott
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Sounds like you need to replace the VSS anyway. However there was a thread on here a couple of days ago posted by firemanpat29 in which subford said the problem was a bad fuse or fuse connection. The guy checked it out and sure enough a fuse solved the problem.
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I did read that post and did check the fuses in my truck, fuses are OK and yes hopefully the new sensor will cure the problem. I will be real interested to Ohm out the new sensor to see if there is a difference in values. One thing that I am curious about is that this sensor, the old one, is magnetly based. That leads me to believe that it generates a signal off of the ring in the rear end to provide a reading for the computer. I guess I do not see how this sensor could fail to generate a current for the computer. 
Scott
Scott
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From: metro detroit area...
there is another thing that would cause this issue... the psom (programmable speed odometer module), its a circuit board connected to the back of the speedo. I've read that the soldering in these can be faulty causing resistors and things to come loose. The only problem is that if you can't find one at a junk yard you have to go to a dealership to buy it and they have to install it to ensure you have correct mileage, from what I hear it is around 400 bucks or so to have this done, but you should be able to find one at a yard for about forty bucks. The only other thing I could think of is the TPS (throttle position sensor) could cause hard shifting, but not the odometer going blank and the speedo not working... good luck
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You are right, there is an exciter ring in the diff. This can come loose or break but rarely. However the sensors do go faulty.
There should not be an oil leak so I would go ahead and replace the VSS.
However if it is faulty I would expect your ABS light to be on also.
There should not be an oil leak so I would go ahead and replace the VSS.
However if it is faulty I would expect your ABS light to be on also.
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From: Concord, NC
The ABS (anti-lock brake system) light would also illuminate if the speed sensor is faulty, in addition to the O/D light on the shift handle if the truck has one.
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OK, I changed the speed sensor and it worked althought it is slow to come on at start up. I also pulled the speedometer last night and the only thing I could see was that the transistor with a heat sink appeared to have overheated at some point. I still would like to see a definitive wiring diagram of this system to get a better idea of how it is setup.
Scott
Scott
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From: Easton,Ks
OK, I changed the speed sensor and it worked althought it is slow to come on at start up. I also pulled the speedometer last night and the only thing I could see was that the transistor with a heat sink appeared to have overheated at some point. I still would like to see a definitive wiring diagram of this system to get a better idea of how it is setup.
Scott
Scott
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