P0420 code

[jtz54]

Getting an intermittent P0420 code. Hooked up a live ODBII scanner and B1S1 seems stuck at 2.2V while B1S2 seems to fluctuate normally 0-0.8V. Seems to indicate that the front (pre-cat) O2 sensor is bad. Cat temp reads 800-1100 degrees. Am I correct?

Thanks!

[3linkedchevy]

Alright, got a P0420 code in my girlfriends 2008 Rogue last weekend. This past Saturday we were driving it, the check engine light went off, about an hour later sitting at a red light am the car died. Put it in park, cycled the key on and off, fired right back up and no issues. Yesterday (Sunday), started no problem twice within 30 minutes when I moved it in the driveway. So fast forward to this morning, my girlfriend went to leave for work and it wouldn't start.

One of the possible issues I saw besides a bad catalytic converter was faulty plugs, I had been procrastinating about doing, so 8am this morning I put new Bosch Iridium plugs in. Still no starting, tried jumping/charging the battery off my truck, no luck, had the battery tested, it's good. Went to the dealership to pick their brain, one of the techs without hesitation said it's the cat, and they want the better part of $1200, that's a big nope since I am pretty mechanically inclined. Pulled the 1st O2 sensor and it looked pretty bad and wouldn't start with it out.

So for the hell of it I put the O2 sensor back in, tried starting it,just the same cranking and wanting to turn over. Hooked up the jumper cableS again, let it charge the battery for awhile. Got in, cycled the key a few times, tried starting while I was pumping the gas, took a couple tries and it fired up. Let it idle for a few, shut it off for a few and it started right back up. Let it sit for about an hour and it fired right back up, drove it around the neighborhood and drives fine, the new plugs really helped.

So about a year and a half ago we had it smogged in CA (in TX now)and the smog guy said all the numbers looked very good. So I am skeptical if it's the cat or not, but maybe the fuel pump starting to go out?

I should add, the car is about to hit 195k miles.

Also, sorry for the long post and if this has been covered some where else before and I overlooked it

[Rogue One]

P0420 NISSAN ROGUE - Catalyst System Efficiency Below Threshold Bank 1
Tech notes
As the code description implies the P0420 code means that the vehicle's control module has detected that the three-way catalytic converter is not working properly (is not as efficient as the factory is expecting). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases the catalytic convert needs to be replaced to fix the problem. If the P0420 code is combined with other codes, try fixing the other codes first.

I had this issue for many miles. My mechanic said my cats were fine. The O2 sensor was a tad too sensitive and was throwing the code every few hundred miles.

I fixed it myself for less than $5.

I bought a spark plug non fouler

Widened the fouler out with a 1/2 inch drill bit.

Screwed the O2 sensor into the non fouler.

Screwed the whole stack back onto the exhaust pipe.

TIP: Unhook the electrical end of the O2 sensor so you can freely screw the things together

I reset the ses light and drove almost 10,000 miles and never saw the code again. The car subsequently passed PA emissions with flying colors.

It works because it holds the O2 sensor slightly out of the line of fire. If your Cat really blows, it should foul the O2 enough that the sensor will pick it up.

DISCLAIMER: This worked for me. If you do this and die, it's not my fault.

[jtz54]

Hmm. Sounds logical and worth a try. Thanks!
Where did you pick up the spark plug adapter?

[Rogue One]

I didn't. If you'll note, I was quoting someone else. In this case it was on a different forum. Sorry I can't be of more help.