SmokinRam

Well I keep getting the infamous P0420 (Catalyst Efficiency Low Bank 1 Sensor 1) and we all know thats the one closest to the firewall on the passengers side. Well I can see it from the top and the bottom but cannot figure out a good way to get it out. I have an Oxygen sensor socket that fits it but its too tall and I can't get a ratched on the socket.

Does anyone have any tips or tricks to getting this one out? I am going to put in a new sensor and a fouler and see if that helps.

Thank You

TDGrant

TDGrant

Les7311

Am also have same code.
250k miles. 2011

share a pic or instructions how you removed yours. Are you also consider replacing the Bank 1 catalytic?

SmokinRam

The videos provided were for the older Maxiima's which are much easier. Mine being a 2009, I had a heck of a time getting to the rear (Bank 1 Sensor 1). That sensor has a shield around it which makes it almost impossible for any good O2 sensor socket to fit down into and onto the hex so I had to cut the wires close to the top and put a regular thin walled socket onto it. But it got worse from there. Once I was able to start turning it loose it seized up on me so what I had to do was use an impact socket and I welded a long piece of flat stock to the side of it and loosen it from under the car. Took two of us. One resetting the socket from above and one under the car turning it loose. It was tight the whole way out and in fact damaged the threads. Overall took probably 2 hours to get out and then I had to clean and tap the threads in the cat itself for the new sensor. Horrible job.

Now what I did after that to try to eliminate these codes is put spacers on both upstream sensors, front and back. Well my intentions were good but now I am getting slow response codes on both sensors. Oh yeah before I forget, make sure when replacing these sensors you use only OEM Denso sensors. The cheap ones will throw all kinds of codes. So now I am waiting for my next free moment to remove both o2 sensor spacers and install two new OEM Denso sensors and see what happens. I've replaced o2 sensors on cars for over 20 years and have never had issues like I am having with this car. I am hoping removing the spacers and new Denso sensors solve the problems.

Hope this helps you out.

Les7311

great feedback. I think your post is the only one that talks about this code for our Gen. on this forum

you’re correct about the shield that prevents the socket to drop over the sensor - did a bit of pulling down the wiper cowl to access from top - the wrench didn’t fit.

so for now it’s replacing the Sensor. Any plans for the Catyl replacement? Found this on the tube



keep thread alive..

SmokinRam

As of now I am doing everything I can to not have to change the Cats. Looks like it could be a pretty intensive job. Being a 12 year old car with 104k miles the manifold bolts and nuts are pretty rusty. Definitely not a job I am excited to tackle. LOL

I am going to try the sensors now and see what happens. Should have an answer in a week or so and I will post the results.

Les7311

Kewl. Am following you closely.
my uncle is suggesting replacing both sensor and Cat same time and a “piece of cake”. Well he has a mechanic, lift and all

I did the lacquer thinner - one gallon, and in next tank fill with the CataClean

Neither worked, except slow down the check engine light frequency which I clear on show.

I do notice: on full up, the gas range say ~400 miles. On way to work 50 miles, the range jumps to 440. Shut off, am back to now 380. (Just as example).

One theory shared that the purge valve could also throw the 0420 code???

I get about 420 on a full tank now, used to get about 450

SmokinRam

I never heard of the lacquer thinner trick but I did try a bottle of Dura Lube Cat Cleaner from Amazon and like you said all it does is slow down the frequency of the engine light.

Now the Purge Valve, that is interesting. I've never heard of that causing the P0420 but its worth a look for sure.

Les7311

Yeah, kind weird in the PurgeV theory.
not a nice access job, but found a tube DIY. I over top-off at the pump by another gallon post initial “click”

The cat, O2 sensor, and exhaust pressure leak, mass air flow are all culprits.
if a shop can perform the test individually, that should rule out the listed. Trying to find one locally is hard here

use liquid wrench spray down overnight before pulling them rustied bolts

Bificus99

Or PB Blaster, really good for rusty exhaust bolts!

Les7311

you will find this funny

D-low beam died last week… 2hours surgery Monday and $20 (eBay bought) later, now starts the TPMS flashing, and a leaking upper radiator hose (surgery this weekend)

drove car like a bat-out of hell last two days on full tank and dialed 460 miles (wow…. Remember used to be w daily Pcode ~400 miles)

no Pcode since replaced D low beam ( what’s that all about??))

do you think our temperamental Max is seeking usual attention? 🤣🤣. Knocking on wood, but code will be back… no correlations obviously but I may have to find another fix to stage away that code 👀🤔👀🤣🤣

Les7311

this blue leading down, is this the crusty Bank 1 sensor in question