O2 sensor

CEL came on my 2003 toy extended cab.. AutoZone checked it and said it was on exhaust, but there was 2 of them. Said it probably was the one before the catalytic converter. $100. Can't they tell which one it is and do I have to reset something to cancel light out or will it just go out.
Thanks

 

I just recently replaced both of mine. If memory serves one is 100 and the other is like 50 ish. Might consider just forking up the 150 and doing both and being done with it. I did my upstream due to a CEL and the other one popped a code not even a year later. You might have better luck than I did but it’s something to think about.

Do you know what the specific code was ?

 

I just realized a read your question wrong.

My bad.

In theory The light should go off on its own once your truck runs its little internal diagnostics scan and realizes the problem is gone. It’s my understanding that Toyota likes to run its scan between 40 and 60 mph at duration of 10 minutes if possible. The easiest thing to do would be for you to go back to AutoZone and ask them to clear the code

 

You could buy a cheap code scanner and check and reset yourself for $23:

for Android Phones ONLY - Wireless Bluetooth Diagnostic OBD2 Scanner Car Code Reader and Scan Tool for All 1996 & Newer Vehicles ELM327 Compatible OBDII

https://smile.amazon.com/gp/product/B005NLQAHS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

The one linked is for Android, but they make them for Apple too.

I had a similar issue but it was the *rear* sensor.

 

The code says PO135 02 Heater Circut (Bank 1, Sensor 1)
I have done a lot of mechanical work but never replaced one of these. Do they come out without a lot of trouble and not destroying anything else. Is this something I can do myself or does it have to be on a hoist and heated to remove.
Thanks

 

https://www.youtube.com/watch?v=WXX8DXsNx3Y

that code will clear itself. To verify, unplug your old and plug the new one in and start her. You want a little heat on the nuts so this is a 2fer. Replace the gasket too or other codes will pop later on.

 

To remove them, soak the bolts in BP blaster (or any other product that does the same) for at least 12 hours. It will really make your life easier since those bolts will be easier to take off in that tight space they are in.

Also, buy the real deal here. Don't skimp out and go on ebay for the 48 dollar ones they have on there. Trust me, I did that and received one that looked genuine with denso markings and from the "Toyota/Lexus factory" packaging and all. It was a fake and it caused my check engine light to start telling me I had a bad MAF sensor (which I did not) and also give me random engine rumbles when in idle. Looked on this website and others had the same issue with one even having the exact same fake I had bought.

Needless to say, I returned it and went out and got a real denso one from a reputable seller (rockauto, nappa, etc. ) for about 115. If I had known I was going to deal with that whole fiasco, I would have forked out the 115 then and there.

 

I had a lean code and noticed I still had the factory o2 sensors so I ordered a new upstream from rockauto. Turns out it was just a cracked vacuum hose. So instead of returning it I just soaked the nuts in Pb blaster and installed the new one. Pretty easy 30 min job for me. Both are denso sensors. The one that came out was a bit fatter on the end and had Toyota denso printed on it. It was still functioning fine at 219k miles amazingly.

 

Which hose? Replaced my downstream for a 0136 and still have a code after 300 miles.

 

I had a p0171 and it was the rubber hose that connects on top of the upper intake manifold. It runs to one of the sensors coming off of the charcoal canister. The backside facing the firewall was split about a 1/4inch max but it was enough to suck air and toss a lean code. Did you happen to check to make sure the electrical harness was clean when you plugged in the new sensor? Could be a wire issue, exhaust leak, vacuum leak, faulty sensor too. What brand o2 did you go with?

 

I actually had the p0420 pop up today. Now I’m wondering if I need to replace the rear o2. The cat is new.

 

imho, I would reset the PCM and drive it, wait and see. The P0420 code is not an "instant" code, meaning that it takes a series of tests over a period of time to set it. If you have an OBDII scanner that can display live data you can watch the voltage signal from the rear o2 sensor... it should be pretty flat, indicating that the CAT(s) is/are doing its job of storing oxygen.

 

I reset it and it came right back within 30 miles. Just funny it threw it literally 30 miles after replacing the 219k mile upstream o2. The rear o2 looks to be factory as well. The cat was replaced less than 10k miles ago. I don’t think the new sensor and the 20 yr old rear one are getting along. Truck still runs flawless, I have a plug in scanner I can watch live data on. I think the rear is suppose to stay at 0.45 volts

 

yes and stay pretty flat. URD makes a "gizmo" that plugs in between the factory harness and rear o2 sensor and all it does is make the signal flat, esentially fooling the PCM into thinking everything is ok. For my Tacomas in mexico I have them installed. There is a write up on the forum where you can build your own for under $5 but you have to wire it in and if is isnt done descreatly and cleanly a decent smog tech will spot it and flag it. With URD, you can unplug it down the street and pass smog then reinstall when you get home.