# P0420 Code - 2007 Sentra 2.0S



## Thomas7399 (Jan 18, 2016)

Hello all,

I'm getting a "P0420 NISSAN - Catalyst System Efficiency Below Threshold Bank 1" code and light from my 2007 Nissan Sentra 2.0S.

I've had this light on and off for the past 4 months or so. I've done some reading on this code, and it sounds like it could be the catalytic converter. I am a complete Newbie when it comes to maintaining cars. What steps do you all recommend I take? Should I start by replacing the O2 sensor?

Thanks


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## tristanlook67 (Dec 28, 2015)

It's probably the 02 sensor unless it has alot of miles my 2004 altima has 190,000 miles and I just had to replace my catalytic converter it's a common problem on these cars

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## cj1 (Oct 21, 2014)

See if you can't check the engine parameters for normal operation before changing cat or O2 sensor. 
There is a warranty period for converters maybe up to 10 years. Check your specific case.


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## Thomas7399 (Jan 18, 2016)

Thanks --- what do you mean to "check the engine parameters for normal operation"? Is there a specific test that I need to run?

Also, you mention a 10 year warranty on the cat converters. Is that capped by mileage? Is that through Nissan?

Sorry for the newb questions --- thanks in advance.


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## quadraria10 (Jul 6, 2010)

I will add that ignoring a malfunction indicator light for 4 months is a recipe for a much larger repair bill down the road. It could have been a bad 02 sensor. You don't mention mileage, but NTK who makes the sensors for Nissan suggests they have a service life of roughly 100,000 miles. As they are key to providing burn info for regulating fuel and air mix, a bad one will usually have you running rich and using more gas than you should be. This tends to affect your catalytic converter after a while as unburnt gas gets into it. If you then let that fully go, in some Nissan's the material in the cat can start to break up and get sucked back into your engine and then you can have serious engine problems. Almost everything in your car works together, ignoring things as they need repair usually ends up damaging something else.


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## cj1 (Oct 21, 2014)

OP - there is a engine health test based on engine parameters that is used to diagnose problems. A shop can do this for you or with a live data scan tool and some engine knowledge you can do it yourself. 

The point is that a poorly running engine can contribute to the early demise of the cat or sensors.

The cat warranty is from Nissan and i believe 8yrs/80,000 is mandated by the Feds and some states may have up to 10 years/100,000.

Cheap temporary fix for the Cat giving a P0420 has been to standoff the post cat O2 sensor with a spacer, lots of info out there on this. Can't say if it will work in your case.


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## Thomas7399 (Jan 18, 2016)

Sounds good; thanks everyone for your responses


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