just finished replacing my cat after welding and sealing all exhaust leaks, now the car runs so smooth, except just for the p0171 code (which i believe is the afm sensor) so i kinda figured i had to change the downstream sensor cuz it looks beat up n worn also
i have a universal o2 sensor which i originally bought for the bank 1 sensor 2 (by radiator) but found an oem replacement. want to know if there is a difference between downstream and upstream sensor, are there different levels of voltage or heat sensing? i believe it uses same for wires 1-signal 2-ground and other 2 wires are for heated just not so sure on specs
wish my laptop worked cuz i have a usb obd scanner so i can get readings from the sensors

 

k , i was just told that the universal will fit upstream and downstream as long as it has 4 wires, just would to hear that again as a 2nd opinion to make sure, if not i can get the oem for exact fit and avoid the troubles of trying to fit it which would not be a problem with soldering etc..
where to get access and unplug the downstream sensor is what im trying to figure out? from interior?

 

Just a small correction to your post. The bank 1 sensor 2 is near the firewall not near the Radiator

 

You may already be aware of this, but just to save yourself some money, a downstream O2 sensor (after the catalytic converter) is not a vital sensor. It's basically just an emissions requirement that tells the owner if their catalytic converter is working or not. It doesn't tell "tell" the engine's computer to do anything different, whereas an upstream (before the cat converter) is VERY important because the engines computer uses that info to determine the air/fuel ratio.

A downstream O2 sensor's main purpose is for emissions inspection, to just tell the inspector if the catalytic converter is working or not by lighting up a "check" engine light. Earlier OBD 1 cars didn't have this sensor, and many people who "mod" their cars and remove their cats just put a resistor in there so it won't send an error message.

Your car won't run any different as a result of this sensor, so you might even want to just find a cheap used one or solder in a $1.00 resistor and save yourself from using your new $150 O2 sensor.

 

In my lexus a bad O2 sensor causes the VSC to turn off. If you want your VSC to function install the proper sensor.

 

dcapo:
can you provide details of the replacement cat you used. the oem is quite pricey. what needs to be welded?

 

ok yeh thanks for confirming that, its what i had figured in the 1st place, i will try the universal one i have
so would the pre-cat sensors tell u if your car is running lean/rich or would that be the afm sensor or could it be either one cuz i got the p0171
i was also told i needed to reset the sensors, by computer or scanner tool?
I used a brand new cat from a 00' Infiniti i20, which I got online for 35 bux w/shipping. It shot up to 150 after I bought it so I guess I got lucky. Unsure but i think it was inlet/outlet size 2.5 and dimensions 13x9x6.5(not exact fit for the es300). Stock piping for es300 is 2.25 or less but definitely needed adapters and trimmed pieces to fit stock piping which had to be welded together. I used a 90a arc welder I bought from harbor freight for a buck, not too strong but got the job done and no leaks at all tho. Had to also prep-sanded then grinded down a lil to smooth weld. I put in overnight hours to complete this. Was easier for me to remove damn near the whole exhaust system from cat to muffler(2 14mm bolts flange connecting cat-to-downpipe, o2 sensor, and 3 rubber muffler hangers)

This is by far, not the easiest task I've done for this car. Due to working conditions. Difficult, when u don't have a garage and youre working outside so its very cold and snowing, and of course the popo's lol (for welding, but they gave me a break cuz they knew I was grindin'). Could've taken it to the shop to get it welded to save money/time but I wanted to brush up on my welding skills plus to own my very 1st starter welder. Which I know I may need for future projects anyways.

 

ok thanks i just get confused on technical terms sometimes

bank 1 senor 1 is by firewall
bank 2 sensor 1 by radiator on header



bank 1 sensor 2 after cat

 

PROBLEM SOLVED FOR P0136 which was the o2 bank 1 sensor 2 which I replaced with a universal one. Had to remove driver seat to unplug the connector. then unscrew it from underneath the car. Rewired/soldered it and works like a charm.

Just down to 2 codes, a p0325/p0330 which are knock sensors or wiring. Which I will do on the weekend and pull apart the intake manifold in order to get to it.

 

Is upstream two oxygen sensors are located on Sensor 1 on Bank 1 and Sensor 1 on Bank 2 and downstream is one oxygen sensor located on Sensor 2 bank 1 after catalytic convertor ?

Also are the two upstream 02 sensors identical ?

I have Bank 1 Sensor 1 error code p0130 coming on my 1997 Lexus ES300. I am confused which one to buy .

I want to buy denso oxygen sensor which is having 2 types of 02 sensors

Model # 234-4622 - for upstream ( 2 required )
Model # 234-4137 - for downstream (1 required)

Please help.

 

I think it goes Bank 1 Sensor 1 is behind the firewall, Bank 1 Sensor 2 is by the Catalytic Converter