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Ron Z.
Ron Z., - Toyota Tech -
Category: Toyota
Satisfied Customers: 19052
Experience:  18+yrs experience. State Inspector and Toyota Diagnostics
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I have a 2004 Toyota Avalon XLS and I need to know where the

Customer Question

I have a 2004 Toyota Avalon XLS and I need to know where the B1, S1 sensor is located. Also, is the B1, S1 the "Primary (upstream)" air/fuel sensor, or the "Secondary (downstream)" oxygen sensor? Would like a diagram if possible.
Submitted: 2 years ago.
Category: Toyota
Expert:  Ron Z. replied 2 years ago.

I'm sorry the Tech you requested was unavailable to assist you today. It appears that Tech is currently "Offline". Now that his 15 minute "request lock" has expired, hopefully I can be of some assistance in his place...
The A/F Sensor for Bank1/Sensor1 is mounted to the exhaust manifold on the side of the engine closest to the windshield. Best access will be from under the vehicle working upwards - CLICK HERE for an image view. Make sure the inspect the electrical connector and wire harness for any loose, broken or damaged wires before replacement. The B1S1 is the "primary" or "uptream" sensor. It is an "A/F? (air/fuel ratio) Sensor and NOT an Oxygen Sensor, so make sure the replacement part is correct. I've found Bosch replacement A/F Sensors work quite well on Toyota vehicles. Please remember to leave a rating using the rating system at the top of this page or accept the answer so I may be credited for this Q&A. You can ask follow-up questions any time, even after you rate or accept.