What causes the OD off light to flash on a 2003 Ford Explorer?

Answer 1

The powertrain control module has detected a malfunction , have it checked

out . (Helpfull)

I have Ford Explorer MY OD off light kept flash to I took to mechanic He said might be sense malfuction not to worry about it..

Then 5 month later something was happening I hardly had no speed to drive or climb a hill then made loud noise some thing was pulling.

I took in to mechanic to check it out he said my OD should been on I didn't know that cause i didn't have booklet..then he check out tranmission fluild was fine then he check on tranmission he said my tranmission is gone..He did say my OD should be on when you have OD off driveing over 45 mile hrs on highway that you could be burn up your tranmission having OD on off.