I drove my 95 4runner for about 400klm one day and I blew my main seal to my tranny...dumping out tranny fluid as I hobble to a shop.It seemed like I got excessive heat in that area cause we couldnt see why this seal went on me at 70,000klm on the car. Also had no power since I bought it...made me think to change my cat and exaust since I needed one anyway, and it wasnt clogged. Next I changed my fuel filter and that gave me a little more power. Now Im thinking its my O2 sensors....any suggestions why my check engine light went on after I got my seal fixed...o2's mabey???

 

O2 sensors going bad will cause a CEL, as well as possibly causing it to run poorly. The computer uses the O2s to monitor the exhaust makeup, and when they go bad, they are telling the computer the wrong thing. you said that you have a CEL, have you ever had it scanned? you changed the cat, so i assumed that you tuned it up as well?

 

I too have the CEL on. I started off with the idea of changing the plugs in my 2000 SR5. Decided I would also clean the throttle body. Used the wrong cleaner which caused the CEL to come on. I had it scanned and it shows "right bank #1, too lean" and was told to change the O 2 sensor. So to be safe, I changed both sensors, the front (before the CAT) and rear, after the CAT. The next day the light is on again. I scanned it again and the same code is coming up. I am at my wits end!! Anyone have the same problem?

 

fmatexas, check the wires and connector on the sensor.

 

I know these messages are quite old but.... I have been having the same problem with my 2000 4Runner LTD.( CA Emissions)I changed the O2 sensor in the front and then found out it was finally the MAF sensor; it just needed to be cleaned. Then I threw a code PO420 saying something now is wrong with my CAT. ANy suggestions or can you tell me what you did to fix your problem?