So I am getting the Check engine light on and the only code that comes up is P0766. Which that code is the solenoid D in the transmission. The fluid is clean and looking good. The level was full. I pulled the pan and pulled the solenoid out and it read 11.7 ohms. From what I could find online the range should be 11-15 ohms. I also applied 12v power to it and I could hear it click. So it makes me think it is ok. it will not go into overdrive with all this going on. I know that if you have issues with o2 sensors and other things it will cause it to not go into overdrive, but i am not getting any other check engine codes. Is the solenoid really bad? Any one have similiar issues? I am stuck. Thanks in advance.
It is a 2003 RX300

 

first welcome aboard. Can I ask a little history, How many miles and when was last transmission fluid change.?

 

The reason I asked the above is you may have contamination is the valve body of the transmission causing it to not operate properly. I would perform a fluid and filter change. Than maybe a second drain and fill of fluid and see if it helps. If the fluid has been changed often than you might try a fluid exchange with a transmission cleaner added to free things up. The chances of the solenoid not working are slim, however what the solenoid operates (pistons in the valve body) could be sludged up from either contamination or a clutch or gear failure.

 

The vehicle has 119700 miles on it. It was flushed about 3 months ago at a transmission shop. When I changed the fluid it looked really good. I am not sure how things looked before the flush as this is the in-laws car.

 

Same new valve body and new solenoid still setting code.any suggestions

 

Try adding some LubeGard Red.

 

I have same issue and code and my S4 solenoid is functional, as well. With mine, the O/D button now engages/disengages engine braking. When yours was refusing to engage 4th gear, and you pressed the O/D button repeatedly, did it engage/disengage engine braking, like it does on mine? Were you ever able to solve the "no 4th gear" problem?