Hi everyone. My 1999 ES300 has just started throwing a CEL, and the OBD-II scanner reads: "P1133 Manufacturer controlled air/fuel mixture sensor". Unfortunately, it does not say which one. But, I scanned the posts and found that P1133 is Air/Fuel ratio Sensor Circuit Response Malfunction Bank 1, Sensor 1.
Apparently, Sensor 1 is an upstream sensor, in the exhaust manifold before the cat. But, is Bank 1 the firewall side or the radiator side? Is this a DYI (from the top or from the bottom), just unplugging and replacing the sensor?
Thanks for your help.