I am a newbie to the lexus game and I just purchased a 99 GS 300. When I was driving home I noticed the rpms were at 4,000 at 70mph and didn't think that was normal. It looks like it will not shift into overdrive. All there other gears shift smooth and fine. I do have CEL but it is P0446 Evap Error. I also noticed the gauge cluster has a M for m mode witch my car is not equiped with and I was wondering if the wrong gauge cluster would be causing it not to shift into overdrive. I wouldnt think the cluster would cause it but im not sure. Can anybody give me some advice.

Thanks

 

Make sure you are not in D4. This car has 5 gears. Change ur tranny fluid see if it helps

 

I changed the fluid and still does the same thing.