O/D Light flashing and not changing into overdrive

[Vorby]

Hi,
I've got a 1995 auto Isuzu mu and recently the O/D light on the dash has started flashing and it wont change into overdrive when cruising down the freeway at 100km/h.
It only started doing this since i've recently had the timing belt and a big service done where all the filters in the engine were change.
I was just wondering if anyone's got an idea whats going on.
Cheers

[geeves]

This has come up before and is from memory electrical and took a long time to find. If it started after the service then go back to your mechanic and tell him he broke it.
I think it was a loose wire on the trans but not sure

[Vorby]

I took it straight back and told them what was wrong. They've got it at the moment and are working on fixing it. I was just curious as to what might be wrong with it.
thanks

[jezza]

At a guess I would say the mechanic removed the wrong screw from the back of the gauge cluster to turn the timing belt light off. If it is he removed the dash speed sensor earth which will bring up the transmission fault light because the speed sensor on the trans is reading differently to the dash sensor. I know this becuase it happened to me, and it took a long time to find out why

[Vorby]

Thanks for that. That was exactly what was wrong