The OD light is flashing on my 95 explorer.
It has 171k miles on it and the tranny was rebuilt 20k miles ago (off warranty).

I got DTC 648 - incorrect gear ratio for 4th gear.

I reset the computer and the tranny shifts fine, but when its supposed to switch to the 4th gear the flashing starts.

If I reset the computer and run with the overdrive off, I don't get any flahing plus the tranny shifts smooth. Dont get the 4th gear, though (not supposed to, i guess)

I wonder if the problem could be a bad solenoid of some minor issue. Because the tranny has been rebuilt not long ago, I dont thing it would be all screwed up again. When it was rebuilt I asked the mechanic to keep the old solenoids, since the didn't read any errors and I was short on money.

I also got the following codes:
DTC 116 - Coolant temp. sender out of self-test range
DTC 167 - Insufficient Throttle Position Sensor (TPS) change during Dynamic Response Check
DTC 326 - EGR voltage lower than expected
DTC 332 - EGR valve opening not detected
DTC 335 - EGR voltage out of range

I've read in a previous forum that the TPS might be causing it (thanks to CNTHOR), so I will replace it and post the results.

Meanwhile any similar experience and possible causes / solutions is highly appreciated.

 

Sorry for the long post, but I guess any info is important :-)

 

Here's an update:

I changed the TPS, ECT, and EGR. All the codes are gone except for the DTC 648.
I guess the problem is inside the tranny, hopefully a solenoid only.

I will try changing it before I go for another rebuit. But until then I will keep driving with the OD off, since it doesnt require 4th gear (overdrive) and therefore the OD light doesnt flash.

Anyone knows where I'd get info on replacing the solenoid for the 4th gear???