Hi all I have owned my GS300 Mk1 for 2 years now and the other day my Speedo stopped working and the overdrive light keeps flashing.
Can anyone Help me out point me in the right derection what can it be and where is it located ect,ect. I would be gratfull for any help anyone could
give me. Many Thanks Joe

Sounds like speed sensor from gearbox. You need to confirm the error code off the ECU - look around for information on your engine code (2JZ-GE) and the correct procedure for using a jumper on the diagnostic port under the bonnet. It flashes a sequence that you can decode.

There are two speed sensors on the 2jz-ge, one for the transmission, one for the cluster.

Sounds like this fault code 42 from the link link to FAQ on error codes

Speed sensor probs are not expensive, and just probably bad connection or bust sensor.