I have a 2000 RX300 with 36,000 miles on it. I recently had the check engine light go off and when I took it to my local Toyota Dealer they told me that I had a bad AF B1 S1 sensor and that it needed to be replaced to the tune of 415.00 What does this sensor do? Are they referring to the MAF Sensor or the O2 sensor? And if it is the 02 sensor should I get both of them replaced or just the one. It seems to me like they are charging too much for this sensor. Is this a fair deal for replacing the sensor? The Part Number they gave me is 89647-48011. Any help would be appreciated. thanks

 

What was the cel codes? Find them and run a search.

But for the maf, just uncrew the two screws on the maf sensor and gently lift it out, note if dirty and then carefully clean. I've posted about this. Do a search.

http://www.troublecodes.net/Lexus/

 

af b1 s1 is the AIR FUEL sensor bank 1 sensor 1

on the motor its on the bulk head side first sensor. go to auto zone or some parts store and ask them for a air fuel sensor for ur car. toyota uses bosh. its easy to do ur self if u want to get dirty

u need a 02 sensor socket or a 24mm wrench

 

O2 sensor would be the more generic name.

 

there is slight differences but if u put an 02 sensor where an a/f ratio sensor ull get cel codes

02 reads oxygen levels in the exhaust with readings from .01 to .99 v

a/f ratio sensor also reads like an 02 sensor(wide band type) but its range is +/-3.3 v

lexus started using a/f ratio sensors because it helped with lowering emisions and faster response with more accurate readings in the exhaust stream.

http://www.autoshop101.com/forms/h37.pdf#search='air%20fuel%20sensor%20ratio%20sensor'

 

Great link!