Where exactly is the bank one sensor one located on my 2003 Toyota Avalon? I know it is near the firewall but I can't quite locate it. Once I get it out, how do I test it to make sure it is the issue without spending over $100 for a new sensor? Thanks JM

hello, the banks 2 sensor is located in the exhaust manifold near the firewall and visible from the top, you will need a special o2 sensor socket to remove it.

The bank one sensor one O2 is located in the exhaust pipe before the Catalytic Converter, bank one is the cylinder bank that also contains the number one engine cylinder, in your car that would be the cylinder bank at the rear closest to the firewall (see diagram below). You will need to raise the car and crawl under it to replace the sensor and you will need a special O2 sensor socket. Remember always use safety stands to support the car when under the car for any repairs.
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O2 sensors location is broken down like this. The bank refers to which side of the motor the sensor is on. Bank 1 is the same side of the engine as the number one cylinder. Bank 2 is the other side of the motor. Sensor refers to either before the cat or after the cat.

Bank 1 sensor 1 would be the O2 on the side of the motor that the number one cylinder is on and before the cat.

The number one cylinder is on the back side of the motor (the side closest to the firewall). The O2 sensor will be in the exhaust pipe near the exhaust manifold.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Above is the sensor itself on an 03 Avalon.

If the heater circuit has no activity check the relay located inside the engine room junction box JB shown below.

The bank 1 O2 sensor is one before the catalytic converter. Bank 1 represents the firewall area.

Oxygen Sensor Connector locations

1. Disconnect the oxygen sensor connector.
2. Using an ohmmeter, measure the resistance between the terminals +B and HT. Resistance specification: 11 - 16 ohms at 20°C (68°F).
3. If the resistance is not as specified, replace the sensor.
4. Reconnect the oxygen sensor connector.

Oxygen Sensor testing




I really hope helped with this. Remember rated this help, good luck.

WHICH ENGINE?.. 2.0 four cylinder? OR 2.7 V6?
Anyway, sensor 2 is always 'downstream', so it's lower than all the others. V6? lowest near the firewall.. .4 cylinder?.. lowest near the radiator.

the bank 1 is in the front of your car close to the radiator, the other one is the bank 2. I think you have to replace the bank 1 and bank 2 sensor and the po115 is the coolant temperature sensor, after you replace all these sensors and have the machanic reset or turn off the CHECK ENGINE light. check with the emmission inspector before you begin to replace all these parts. good luck

bank one is the bank closest to the firewall in the manifold but if you replace this one you should do the other or you will get a code for it not long from now because the new sensor will operate much better and faster

In the exhaust manifold on the firewall side. Its not a o2 sensor. Its a AF sensor.(air fuel ratio sensor)
Covered under your 3/36k warranty.