Hi,
I am trying to find more information on oxigen sensors. There are two after the cats as downstream and two before cats the upperstream. Is there any differences in part numbers for upperstream and downstream. What about the connectors and the wiires lenght, is there any differrences in upperstream and downstream?
I checked amazon and see that they selling downstream for $48 but not upperstream. Where could I buy them?

 

down stream typically only tell you if the cat(s) are functioning properly or if they need to be replaced. the up stream 02 is the ones that control or change the engine and how its air/fuel ratio is set... the up stream ones are more important and typically the ones that go bad as they do more work. unless you are throwing codes i would not replace them.

sorry i dont know part numbers or have any more help

 

Yes, I got two codes detected with the scanner: P0420 Catalyst System Efficiency Below Threshold (Bank1) and P0430 the same message for Bank2.
I browsed the forum and folow suggestions to replace the fuel cap, it did not work.
Then I replaced two downstream sensors. It did not work also. The warning lights on the dash came back again.
I was thinking maybe to replace the upstream sensors but can't get information on the part # or another name so I can buy them to replace.

 

Looks like you want p/n 89465. It appears to be the same part for both left-hand and right-hand sides.

http://www.lexussouthatlantaparts.co...roduct=5794277

I used a 2005 GX470 to look this up - you should post your year/trim in your profile so we know what you have.

Chip H.

 

if it happened in cold weather just reset the codes.

ecu looks at the up stream and down stream and if they are too similar it trips the code, cause the one after the cat (downstream) should be different if the cat is working.
if you want to throw parts at the problem you are supossed to change the upstream sensors.
I leave the downstream ones until they fail cause they will be less sensitive that way and you will get that code less, cause it helps make it "look" different to the ecu.

since you changed the downstream, you may want to do the upstream ones as the downstream ones are more sensitive now and likely to trip the code.
still I would reset and see if it comes back, and if it does, then do upstream, if it doesn't then just let it ride.

 

This! Recently had a similar issue with 0430 and I unhooked the battery and this cleared the codes. Mine happened on a cold snap morning a couple of weeks ago.

 

 

Yep. Definitely want the Denso. Don't use Bosch on a Toyota.

Chip H.

 

Sure. I get the Denso sensors only. So as I am looking at the pictures posted I can tell that I used
Denso 234-4261 Oxygen Sensors to replace both downstream sensors.
How about the upperstream, what number on the box refers to the upperstream sensors?

 

Upstream are the same and the downstream are diferrent. My code is gone and pass the inspection yesterday.

 

Upstream is Denso 234-4138 (both sides)

Left downstream is Denso 234-4261

Right downstream is Denso 234-4260

http://densoautoparts.com/find-my-pa...icle-selection

Chip H.

 

Wait a second. Does it mean I installed downstream sensors incorrectly? I used 234-4261 sensor for left and right sides for downstream sensors installation on my 2006 GX. Is there any diffrences between 234-4261 and 234-4260?

 

if I had to guess they probably have different length connectors, cause the rear ones do the same thing. if it plugged in and no codes you are fine.

 

I thinking the same thing... same sensors Just different length of wire. Call them and ask. DENSO

 

I think its wire length as well. Check your installation - if the wires aren't hitting the hot exhaust (or even close) I think you may be OK.

Also - "Left" as you look at the GX from the front, or "Left" from the driver's seat? Neither Lexus or Denso are clear on this, so you might have actually installed them correctly, if they aren't hitting.

Chip H.