O/D Off light intermittent flashing?
 

My overdrive light is intermittently flashing. It was doing this before I wrecked it, but I had forgotten about it until I got it out of the shop today.

So, is this an error code?

Yup it is! It's your shift solenoids going out... There are alot of ways to confirm this, first would be checking your transmission oil wether it's low or dirty. Although given the age of our vehicles, I'd replace them all if they start to act up. There are lots of threads about this already, just do a search and follow...