flashing o/d off light-1999 WS

I have misplaced my owner's manual and I don't know what it means when the "o/d off" light is flashing on the dash. It comes on when I hit about 45 mph. Anyone know what the deal is?

It normally means you have a malfunction and you need to have the transmission codes pulled.
Please report back.

It normally means you have a malfunction and you need to have the transmission codes pulled.
Please report back.

Thanks for answering my question. In other words, my tranny is taking a dive on me, correct? It wouldn't suprise me though. It has 156,000 miles on it and I figure it is about that time when everything starts to break down. I will take it to the shop tomorrow. Thanks again.