I have read other posts on this subject and thought I had my problem figured out, but NOT. 1994 f-150 4x4 5.8 just out of the blue the speedometer, odometer, cruise control quit. Also the transmission shifts hard, especialy into 2nd. After reading this forum I thought it was the speed sensor in the rear diff. I replaced it this morning and still nothing works. WHAT NOW??
Thanks for any help.

 

Check the wires leading from the sensor to as far as you can trace it. Also, pull off the rear diff cover and inspect the toner ring, it could have been damaged.

 

I had to put in a junkyard speedometer board to cure this same problem in my 92 E150

 

Since the odometer quit, it's more likely a power supply problem than a signal loss. Pull the cluster and check the PSOM connector for power & ground according to the wiring diagram in the Haynes manual. If it's OK, your PSOM probably just died.

 

the psom board in the Speedometer is in charge of pulse shaping for speed sensor. Whaen it goes bad you can lose the odometer, speedometer, antilock brakes and cruise control.

 

I have the exact same problem, as of right now FoMoCo is checking my cluster out. If you call a dealer it's 700 bucks for a repalcement needless to say I lost my mind and called Ford's customer service to complain..... Nothing came of that. Unless you have a friend at Ford, get on the web and do a search for speedo repairs or cluster service. I found several sites to repair clusters. Let me know if you need the links, email me at scooter670@ameritech.net I will forward them to ya.

 

A bad PSOM won't affect the ABS. They share the signal from the sensor. And it doesn't "shape" the pulse for the other components - the pulse is generated by the sensor, and that determines its shape. The PSOM performs a frequency shift to output a standard number of pulses per mile (I forget exactly how many) by using the conversion constant.

 

Ok, I'll check the wiring first. Not sure how to inspect the toner ring or what I'm looking for. Please be patient with me. thanks again
Rick

 

Just lift one rear tire (or both), pull the sensor out of the top of the diff, shine a flashlight into the hole, and slowly turn the d-shaft and watch the tiny teeth on the tone ring. If any are missing or if the ring wobbles, you'll have to open the rear cover & pull the axleshafts and carrier to replace it.

 

Do you know anyone with a schematic for the actual PSOM?

 

Contact havack (the webmaster) at http://www.broncodata.com/ . He contacted the mfr. for something, and he may still have the contact info.