2000 Sienna air-fuel sensor

[skriest]

2000 Sienna 1M-FZE engine

The Check Engine light is on and I was able to have a mechanic determine the OBDII codes - P0130, P0135. Both indicate an issue with the air-fuel sensor Bank 1 Sensor 1. I need confirmation as to which sensor this is. There are 2, one on the front next to the radiator and another next to the firewall.

Would just replacing the sensor recitfy the issue or coud it be something additional? There is only 50,000 miles on the vehicle.

Dealer told me that these are not oxygen sensors but air-fuel sensors because it apparently has California emissions. Price from local dealer for just the sensor was $227.00. I don't want to sink the money into it unless I know for sure.

Also, if the sensor is bad what effect is it having on the engine? There is no apparent problems in the way that it is running.

If I do replace the sensor how do I clear the CEL? Is just disconnecting the battery sufficient?

Thanks for any help.