Max9911

Hello,

I have a 1994 Lexus ES300. The engine light recently came on. I took it to Auto Zone for a test (OBD2 test?). Turns out I have an Oxygen Sensor out. It's the "Bank 1 Sensor 1" sensor.

Questions:

Is the "Bank 1 Sensor 1" O2 Sensor the one that's at the front of the car? Or is it one of the others?

Is it the "upstream" or "downstream" sensor (I noticed on Ebay there's the 2 different ones)

Where's the best place to buy these sensors? Ebay has them for around 20 to 30 bucks..

Thank you

DRACO A5OG

That should be the up stream one, bank 2 would be the downstream.

tomf

Bank 1 Sensor 1 is the one on the right side of the engine which is closest to the rear of the car.

Bank 2 Sensor 1 is on the left side of the engine. That's the one at the front of the car.

Sensor 1 refers to an upstream sensor.

Buy Denso O2 sensors. I buy mine from Amazon. The one you need sells for about $48.

ES300NZ

'Bank' refers to the side (or bank) of the engine.

Up stream or down stream refers to the order of appearance in relation to flow.

Therefore Bank 1 Sensor 1 would be on the left side of the engine, the first sensor.

DRACO A5OG

^^^ I stand Corrected.

80es300

The best way to see exactly where that sensor is is to climb a bit into the bay from the drivers side, looking behind the engine, against the firewall towards the passenger side. You'll see the O2 sensor sticking out with it's attached cable. Yes, it appears to be a pain in the butt to get to.

Buy only Denso or OEM sensors. If you happen to have california spec vehicle, you might need Air Fuel ratio sensors and not 02 sensors. Check that.

tomf

This is wrong. Bank 1 Sensor 1 is on the right side of the engine, the bank nearest the rear of the car. Remember the engine is turned 90 degrees in the engine compartment with the front of the engine on the passengers side of the car.

Edit: This presumes the driver's side is on left side of the car. Thanks to 80ES300 for pointing out the geographical location can cause confusion due to different driver's position.

tomf

He has a 1994 model. His model only has O2 sensors. No Air fuel ratio sensors in this model year.

Max9911

Tom,

Do you happen to know the part #? I have an Amazon Prime membership, so I'll definitely buy it there… Just want to make sure I buy the correct one…

Thanks Tom

80es300

On Denso website, it says 234-4622 for 94 es300 but double check.

Tom,
Looks like ES300_NZ is in New Zealand and hence the left/right side confusion. Its best to say that sensor 1 is near the firewall side or as you said side of the engine closer to the rear of the car

Max9911

That does appear to be the one I want on the Denso website… As long as we're sure I want the "Upstream" sensor..

Max9911

Figures… That's the one sensor that isn't Amazon "Prime"…

tomf

I assume the engine is still turned 90 degrees with the front of the engine on the right side of the car. Irregardless, bank 1 is on the right side of the engine regardless of its orientation in the engine compartment.

BTW, I added a clarifying edit to my previous post because, as you pointed out, my description would be inaccurate if the driver's side is on the right. Thanks.

tomf

It shows up as prime for me.
Yes you want the upstream sensor. Denso 234-4622 Oxygen Sensor

ES300NZ

I was still wrong, I assumed the front was the left. Taking left from standing at the crank and going left/right from there. This happens, .. I've been known to be wrong every decade or so my wife tells me.