On my 96 Crown Vic P74, when I drive over 50 MPH the O/D off light starts to flash.

The trans runs fine, shifts fine and only has about 8k on the fluid.

When I shut the car off and restart it, the light turns off but reappears once you hit 50MPH or higher.

I used my Actron scanner and it shows no codes. The scanner at Autozone shows no codes either. I even checked the codes with the engine running, O/D light flashing and no codes were thrown.

I know the flashing O/D off light means something is wrong with the transmission, but I am stumped as to what it can be.

I changed the VSS (vehicle speed sensor)about three months ago but that gave me a steady O/D off light and the scanner showed it as VSS failure. I replaced it and cleared the code and it has been fine ever since.

The speedometer is working correctly.

Thanks all.

Anyone?

When you get your answer, please let me know. I have a 98 P71. Just started this morning under the same condtions as yours.

maybe its a miss fire with the coil or maybe just a sensor is it do anything like bucking when you get up to speed

My brother-in-law just had his trans rebuilt and the OD light began to blink at start-up. Long story short, He now has a second new trans. He was told it means there is a problem with the trans. I would take it to a shop asap.

This is just a guess but maybe it's the trans. fluid temp. sensor? I could be wrong though.

The transmission control switch is a momentary contact switch. When the switch is pressed, a signal is sent to the Powertrain Control Module (PCM) to allow automatic shifts from first through fourth gears or first through third gears only. The PCM energizes the Transmission Control Indicator Lamp (TCIL) when the switch is off. The TCIL indicates overdrive cancel mode activated (lamp ON) and EPC circuit shorted (lamp flashing) or monitored sensor failure.

After searchin around the forums, i'm inclined to agree with you.