Man I could really use some advice here.

My OBD scan tells me an error on my o2 sensor in Bank 2 sensor 1
I am confused by the many different part numbers on the O2 sensors. I have to replace one on my 4Runner the dealership wants 207.99 and I cannot afford that at all. I am looking at after market options but there are so many different part numbers. I also do not understand the upstream
And downstream options. It seems impossible to find the upstream one for the V6 model
If you could please share some insight!!

 

My understanding is that if you use any other sensors than oem it will be a pain in the butt, maybe others can chime in with better info though. Best of luck.

 

For stuff like that, always get OEM.

 

What problems are you experiencing? Drivability problems? An error code from an O2 sensor, if it’s only throwing a solid check engine light, can be pretty unimportant. I drove my 2001 with a CEL and O2 error codes for 10+ years.

 

Yeah it is a flip of the coin on how well it will work for how long have had the best results with the Denso Brand ones since they make em for Toyota however the big if is what one is bad?

 

O2 sensors are responsible for making minute adjustments to the air/fuel mixture. You may not get optimum mileage and/or performance but likely will be so minimal you may not notice. If the check engine light bothers you (it would me) then, as others have said, stick with OEM and just bite the bullet when able.

 

I don’t know where they are on the 4 Runner, but to wdsteven’s point, I put a Denso on my Gen 1 Tacoma like 7 years ago and it’s still working fine. The install was super easy once I figured out where it was.

 

In the 1st gen 4Runner, just lean over the driver's side fender, about centered on the engine, and follow the exhaust down. The O2 sensor is real obvious, right in the center of the top of the exhaust pipe, just after the pipes all come together.
I replaced the one in my 4Runner back when I changed out the head. Just needed a 10mm socket, and a lot of extensions. It's a reach, but with enough extensions, annd a universal just where they get to the socket, you can remove the nuts holdin it in. If it's never been changed, so the nuts have been on for 30+ years, it might be a good idea to soak then with a penetrating oil of some kind. WD-40, PB Blaster, whatever, for a day or two before you try to get them off. Very worst, a nut-cutter is in order. Mine came off easily, but I've read a lot of horror stories about those nuts, being rusted solid to the bolts holding them.

Good luck!
Pat☺

 

I'll second the idea of a good 24 hour penetrating oil soak.

 

Not as difficult as you think...
https://www.rockauto.com/en/catalog...81,exhaust+&+emission,oxygen+(o2)+sensor,5132

https://www.1aauto.com/how-to-replace-o2-sensor-2003-09-toyota-4runner/video/55391


4th gens should have 4 sensors right there. the two upstream are Air Fuel ratio sensors to sense unburnt fuel, the two downstream are O2 sensors after the cats. Sensor "location" should be top to bottom left to right as if looking down at the vehicle from above. Drivers side fwd is Bank 1 Sensor 1. Driver side rear is Bank 1 sensor 2. Pass fwd is Bank 2 sensor 1. Pass rear is Bank 2 sensor 2.