Possible causes

– Faulty Rear Heated Oxygen Sensor Bank 1
– Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
– Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
– Intake air leaks
– Exhaust gas leaks
– Inappropriate fuel pressure
– Faulty fuel injectors

Tech notes

Replacing the Rear Heated Oxygen Sensor Bank 1 usually takes care of the problem.

There is a factory service bulletin for the following Toyota models:
2005