Lexus Rx300 2000 99km Miles Not Shifting Into Overdrive

[daniel5xflr]

In the beginning i had overdrive issues, and the check engine light came on for o2 sensor, so i got that replaced, and it began shifting fine, a few months later the same issue occurred. the o/d wouldn't kick in. the check engine light came on, and it was the knock sensors this time, i kept driving without o/d for about 3 months. so i finally spent 600 dollars on knock sensors and harness, and gaskets. i replaced the sensors, harness, and gaskets. turned the car on and the light was off for about 1-2 mies, and o/d was fine . the light came back on and it won't shift into o/d. and now I'm stuck without a clue as to how to proceed to get the light off, and most of all to get it shifting fine. can anyone help me out, or has anyone had the same issue.?