2002 lexus es 300 with a3.0 liter engine that has a trouble code p0031

2002 Lexus ES300

Question: I have 2002 Lexus es 300 with a3.0 liter engine that has a trouble code poo31 I would like to know which sensor this is ? I failed emission test want to know which 02 sensor needs to be changed Answer: this is a fuel metering problem....if the car is not idling right ..you may need to remove the IAC valve[idle air control] and clean the carbon out of the valve and the throttle body..then reinstall...usually this will fix this code......also check for a vacuum leak