wont shift into overdrive

[xlinkinpark2438]

i have a 94 explorer with auto trans with 30k miles on the trans
and overdrive went out a couple of weeks ago

and i am forshure that the shifter is in overdrive not drive soo dont try that one on me

someone told me that there explorer did the same thing and they got it fixed and it was a bad sensor
Does anyone know what or where that sensor is

any help would be great
Thanks

 

[MrShorty]

3-4 shift is controlled by the EEC-IV computer. It's conceivable that any of the EEC-IV sensors could be at fault. The most important sensors in determining when to shift into 4th gear are vehicle speed sensor (VSS), and throttle position sensor (TPS). However, there are other sensors that play a minor role in this. Best place to start when diagnosing any of the EEC-IV systems is to pull codes (see my notes on pulling EEC-IV codes in the EEC-IV forum).

 

[xcaret]

You should also check the altenator's voltage output ,you need to have good working alt for the trans to shift into overdrive ..at least 13.5 volts .I don't Know the theory on this but after being an autowrecker for 15 years I have ran into this more than once and was confirmed by a friend who owns a transmission shop.

 

[BrooklynBay]

Sometimes the torque converter clutch locking, and unlocking could be mistaken for a 3-4 shift. They both share a common power connection. Check the connector for (+), and make sure your test light is grounded. The PCM applies a ground to activate the solenoids. You could have a blown fuse, or a wiring problem. Sometimes the internal harness goes bad, so check the resistance of both solenoids through that. If the readings of the solenoids through the internal harness are open, or have lower than 25-40 ohms, then the internal harness could have the fault.

 

[peties3]

Where would the fuses be located?

 

[BrooklynBay]

Check the owner's manual for the location of this fuse.