1997 Lexus ES 300 P0150 and P0153 O2 Sensor Codes: Location, Causes, and DIY Diagnosis Tips
Hello everyone, I own a 1997 Lexus ES 300 with a 6-cylinder, 3.0-liter engine. I've been consistently receiving P0150 and P0153 trouble codes from the OBD-II system. These codes point to an issue with Bank 2, Sensor 1 of the oxygen sensor. I recently had the O2 sensor replaced, but the codes persist. I'm trying to understand where this sensor is physically located—specifically, is it situated right after the exhaust manifold exiting the engine? My mechanic claims there's voltage and ground present at the sensor, and he has already replaced it twice. He also mentioned that a new muffler was installed (only the muffler section), not the full exhaust piping. He suggested a faulty Powertrain Control Module (PCM) as a possibility, but I'm skeptical given the age of the vehicle—1997 model with 105,000 miles. Replacing the PCM would likely cost more than the car is worth. The car runs fine and has no noticeable performance issues, but it fails inspection due to the check engine light and these persistent codes. Before taking it to a Lexus dealership, I'd like to get as much technical insight as possible. Are there common causes for P0150/P0153 on this model? Could it be related to exhaust backpressure or wiring issues? Any advice on how to properly diagnose and fix this without overspending? Thanks in advance for your help!
It's highly unlikely the PCM is at fault since OBD-II codes are being set—this indicates a sensor or wiring issue. Bank 2 on the 1997 Lexus ES 300 is located on the front side of the vehicle, and Sensor 1 is typically positioned in or near the exhaust manifold. If there's proper voltage and ground connection to the sensor, it should be replaced with an OEM (original equipment manufacturer) part from a dealership—aftermarket sensors often don as well as fit or perform. I recommend checking for exhaust leaks or backpressure issues after the replacement. Also, ensure the wiring harness is secure and not corroded. Good luck, and feel free to update us on your progress!