mzeitlin

I have a 2000 ES300 with 98,000 miles.

I noticed one of the banks A/F sensor shows a swinging reading from as low as 1.2 V to 4.0 V centering around 3.3 volts. It fluctuates a lot while the car is idling.
The other bank sensor is pretty steady around 3.3 (low of 3.1, high of 3.7 or so).

Is the first sensor failing? or something else going on in the engine in that bank? (fuel injector?)

Thanks