Where is the sensor for an obd2 code error p1155 for Toyota Sienna 2001?

The OBD-II code P1155 for a 2001 Toyota Sienna indicates a problem with the air-fuel ratio sensor (A/F sensor) located upstream of the catalytic converter. Specifically, this sensor is typically found in the exhaust manifold or just downstream of it, before the catalytic converter. It is responsible for monitoring the air-fuel mixture and sending data to the engine control module (ECM) to optimize combustion. If you're troubleshooting this code, check the wiring and connections to the sensor as well.