o2 sensor help. bank 1 sensor 1

Hey all

So on the the next issue with the new truck not that I have the airbag light all worked out.

I am having an issue with a p0420 code and after following the procedure as outlined in the fsm (using an OBD2 scan tool) I am unable to get a signal from the bank 1 sensor 1 (upstream o2 sensor).

I am not certain if this means that it just has no voltage or perhaps there is an electric issue in the wiring leading to the o2 sensor....

anyhow,

Before I go buying a $100+ dollar o2 sensor I was wondering if anyone had an old one lying around (dont care if it is bad) just to test on my truck?

I would gladly pay shipping or if you are local to the washington DC area Ill come get it!


any help or insight would be appreciated.

Thanks

 

Might want to list year and transmission of truck or include the p/n for the sensor...

 

Ok just what did you do??

First that code means that the Cat Efficiency has dropped below what is considered in the range

Does this Have the California Emissions which was the two cats

it is most often the down stream sensor that fails

It can also be anything in the complete circuit

Something as simple as a bad gasket between the cats the O2 sensor vibrating loose .

The wires falling on the exhaust is also common

Wires rubbing through

 

When you do fix it, be sure to clear the code.

I just replaced mine due to faulty heater circuit. Took it for a spin and was hoping the code would clear itself. Drove the same crappy way it did with the bad sensor. Parked it, disconnected the battery, and let it sit while I did a few chores around the house. Hooked it back up and CEL is off, drives fine for the first time since I bought it.

 

I don't know what truck year you have or 4-6 cyl. This fits a 6 banger 04 taco with automatic

$61 Denso 234-4189 Oxygen Sensor

https://www.amazon.com/gp/product/B000C5YCRA/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

 

Sorry I have a 2002 2.7 4cl manual trans.

 

As I stated in my first post. I followed the factory service manual to test the code. I understand that it was a code for a cat efficiency but the toyota service manual has a simple set of steps to diagnose.

the first step was check for exhaust leaks. the second step was to test the o2 sensors. since I cannot get my obd2 scan tool to get a reading from the front cat, but I can get a signal from the second cat, I figured I would start there first.

I the electrical connections of both cats are intact and making good connection and the wires look good and not damaged, along with the sensors being properly bolted down. however I am unable to get a signal from the front sensor.

 

This is a '02 Tacoma 3.4l...

Test the upstream & downstream

Bad upstream...



Good downstream...


FYI...I replaced my catalytic converter and upstream



Good luck!

 

read the toyota docs on how to correctly test bank 1 sensor 1. sensor 1 is always an air fuel sensor

it is not an o2 sensor. the proper name of if it air/fuel sensor, sometimes called
wideband o2...and it is not able to be tested the same way as an o2. it operates
differently and has different electrical characteristics and the docs at techinfo.toyota.com
tell you how to test one. a bit different than simple resistance you can do with an o2 sensor

if I recall correctly
air/fuel is not able to be tested through obdII other than pass/fail or throw
it's own code, such as heater circuit malfunction...it can be tested via techstream and the techstream interface

 

Wonderful response!

Did you also have the p0420 code?

 

Yep. There's some good troubleshooting tips for this code on YouTube. Take your time, and you'll find the issue. The cat can function at 94% and still cause a code.

 

Thanks,

Lastly,
did you go with a toyota cat or aftermarket?

Diagnosis has been slow going because I dont have a physical copy of the service manual so I am trying to do everything online with the copy I found that has everthing listed out of order (BIG PITA).

hopefully I can find some good info on youtube, I havent checked there yet.

 

Aftermarket cat- Autozone has a direct fit or one that you cut & weld. I bought the direct fit for somewhere around $150. Just be careful taking off the bolts. Use Kroil or some real good rust penetrating lube. Exhaust bolts are known to be trouble!!

 

How many miles on your truck?

The upstream air fuel sensor failing at about 150k on the v6 is fairly common. I replaced with a denso I found on an eBay store, don't have that info handy right now, and not sure it would be the same for your 4 banger. If you replace it yourself, be sure to have a die handy to clean up the studs, and some new lock nuts.

 

Bullseye...my '02 3.4L new denso upstream was $150-175, purchased at O'reillys auto parts.

 

My 2.4L Denso upstream was $98 on Amazon

 

http://densoautoparts.com/find-my-part.aspx

Go there, get your part number, search for it on Amazon, done.

 

I just got chasing down a PO420 code. Mine, the issue was the gasket for the rear O2 sensor. Its been a week so far with no code thrown. Before, it would trip every day.

Blows my mind a $1 gasket could cause that much of a headache.

 

I think I am going to order new gaskets for the cat and take it off this weekend to have a look.
mine is a 2.7 4 cyl

 

I have a 2002 2.7 4cyl with 212k miles