Service Engine Soon Code P0420

[dphess]

I had the code ran on my 2002 Altima 2.5s and the code was P0420, catalyst efficiency below threshold, the guy said it's either the lower oxygens sensor or the catalytic converter is starting to go. Which one is it likely to be?

[dphess]

Originally Posted by dphess

I had the code ran on my 2002 Altima 2.5s and the code was P0420, catalyst efficiency below threshold, the guy said it's either the lower oxygens sensor or the catalytic converter is starting to go. Which one is it likely to be?

Well I spoke with the Dealership and they ran my vin # and there are no recals for the cat and I am out of the 8yr/75K warranty on the cat. I have 90K miles on it. It's definitely cat. They want $800-$1000 for the cat and labor.. F that.

Should I get the cat fixed and sell the car. I looked up the cat online and the price for an OE cat was $230 at Advance and Autozone. Should I purchase the cat there and have a mechanic install it

I hate this car anymore. This year alone, the headgasket, radiator went..

[Toolman5523]

Dude, do the smart thing and pawn that heap onto some other poor sap. Yes, your dealership is right in that your cat converter needs replacement. However I'm sure they also failed to mention to you what exactly has happened to your cat. For some reason now when Nissan cats go bad they just don't go bad, they start to come apart. Real fast I might add. Here is where it gets real nice. Due to the normal back-pressure of the engine the cat material is sucked back inside the engine where it then mixes with the oil. When it does that it changes the oil into something similar to lapping compound, and proceeds to eat the engine up from the inside out. Since it mixes with the oiling system you can never get it all out, pretty cool huh. I know this may sound crazy to you, however I have changed dozens of these engines for that very same reason. Trust me SELL THE CAR WHILE YOU STILL CAN.

[dphess]

I have to get the cat fixed first. I have contacted a few different places, Monroe, Meineke, and Cottman Transmissions. All of them will replace the cat.. I will get the cat replaced, have them check everything else and start looking for a new car. I knew that I should have stayed with Honda. My Honda never had problems like this Nissan has.... I won't ever buy another Nissan again..

[dphess]

Ok,

This is from a mechanic friend of mine. He gave me this info.

These are genuine Nissan parts, which makes them pricey. Also, since they are genuine Nissan parts, they will function as the manufacturer intends. Aftermarket (parts store) cats usually have several shortcomings, and more often than not will result in a steady Check Engine light.

Front cat (in manifold) $355 USD currently in stock
Rear cat (in front pipe) $170 USD about 2 days to order

Note that this is just the price of the parts, including gaskets.

Now I have to replace both cats? I thought there was only one catalytic converter on the car. I need help fast.

[Toolman5523]

No, you don't have to change both cats. the p0420 code is for the exhaust manifold cat, that's the one you have to change. That's the one that has come apart. Simple repair: two nuts on the bottom for the down pipe, remove the alternator, remove mounting bracket, take off the heat shield, and then just remove the exhaust man. It also has a brace on the bottom (1 or 2), mounted on the bottom side of man.

[dphess]

Well I had the cat and O2 sensor replaced this past tuesday. It was replaced with Genuine Nissan Cat and O2 sensor, which were both definitely bad. Here is a pic of a new O2 sensor and the bad one. The total for everything was $630.

[FixUrNissan]

Very nice O2 sensor..lol. Now that you have the Catt replaced, along with your beautiful new O2 sensor. Monitor engine oil level. See if engine is burning oil. IF it is the the debris from the catt has contaminated your engine and is eating it away. Gl..

[dphess]

Originally Posted by FixUrNissan

Very nice O2 sensor..lol. Now that you have the Catt replaced, along with your beautiful new O2 sensor. Monitor engine oil level. See if engine is burning oil. IF it is the the debris from the catt has contaminated your engine and is eating it away. Gl..

It's getting an oil change tonight. Should I have them check the oil for debris? As posted before this year alone on this car. headgasket, radiator, cat, o2 sensor..

If I notice debris in the oil, should I begin to look for a new car? I am not paying for a new engine in this car.. I will sell it before it gets to that point..

[FixUrNissan]

well, you won't see the debris, just check for oil consumption

[marvin_1118]

its not o2 sensor, need to replace ur cat converter to fix ur problem. i use to work for nissan so i know ur problem... hope u will get ur car fix

[cubano112266]

Originally Posted by Toolman5523

No, you don't have to change both cats. the p0420 code is for the exhaust manifold cat, that's the one you have to change. That's the one that has come apart. Simple repair: two nuts on the bottom for the down pipe, remove the alternator, remove mounting bracket, take off the heat shield, and then just remove the exhaust man. It also has a brace on the bottom (1 or 2), mounted on the bottom side of man.

Toolman,

Can I change out the CAT if I have an electric impact 1/2 inch impact wrench? I am hoping to save some cash and do it myself before selling the car.

Thanks

Abe