My wife's 89 4runner v6 auto, was driving with no problems on the highway when the AT Temp light came on briefly and then turned back off. Nothing acted differently, a few minutes later the truck just seemed to go to neutral, and rolled to a stop. No movement in any gear, fluid level correct and new, runs the same, just wont move. Any thoughts? I have a spare trans but am not familiar with the auto trans. Are their codes to check if electrical issue? stumped.