transmission will not shift into overdrive

Check the kickdown cable adjustment from the valve body to the throttle body-

does the 2002 Lexus SC430 have it? I know some about cars but mostly on the older model cars---the new ones have so much electronics and I have not kept up with it? I have also been told it could be the knock sensor or a solenoid? I am trying to get as much info as I can as to what could cause this since I have a friend here that can check whatever things you recommend? Thanks again for any help with this!!! Mike

Let's test the coolant temperature sensor-Lexus and Toyota uses the CTS to control the overdrive operation during a certain temperature

Checked the temperature sensor---no problem there. Any other suggestions?

Also shouldn't some warning light come on since it is not shifting into overdrive at all?

Again thanks for your help!!

Check and test the throttle position and vehicle speed sensors if it checked out-bring it in and have it diagnosed

Thanks--will check
where are you located if I need to bring it in?

I'm in the middle of the Pacific Ocean not on the Mothership

checked all you mentioned and no problems? and still no warning lights on the dash---any other things i should check?

Thanks again!

I've given you all I got I'm sorry-

I took the car to a shop and they ran an extensive diagnostic on the car---they said the transmission valve body needs to be replaced and would run $1500-$2000 installed---he said the part alone was $900?
Does this sound correct?
He showed me on the screen while running the diagnostic the the 5th gear was out---there were no codes found though
Is this very hard to replace

Also does the transmission have to be dropped to replace the valve body or can it be done by removing the transmission pan and filter and installed that way?

It can be done underneath, $1500-$2000 for a valve body don't sound right-too high

by underneath---you mean by removing the transmission pan and filter?

Yes sir-that's the only way to get to it-