Check engine light came on so I checked it with the OBD2 scanner. Code is 135. Everyone tells me this is the code when the O2 sensor upstream of the catalytic converter needs to be replaced (one on exhaust manifold). So, I go to Autozone and buy the universal unit. I install it, clear the code, drive it, and the light comes back on is a matter of 5 miles. I then thought the new one may be defective. I then exchange it and the light comes back on.

Now I'm thinking that the universal sensor may not be so universal. I purchase an 02 sensor from the Toyota dealer, install it, clear the codes, and go for a drive. Now it took about 11 miles before the check engine light came on.

Any recommendations before I take it to a professional?

Thanks.

JON.

Maybe you should check the downstream sensor...the computer may be giving you a false reading telling you that the wrong sensor is bad.

It's a heated sensor and the indication is that the sensor or the harness wiring for heating the sensor is malfuntioning. Since you've replaced the sensor then look at the harness for obvious breaks or connector looseness and check the line voltage of the harness heater wire.