# OBD II code P0420



## MikeP8685 (Jan 12, 2010)

Hi everyone, I'm new to the forums and I'm looking for some advice.

I have a 2005 Altima 2.5S auto with approximately 112,000 miles. The car was driving fine and all of a sudden about a month ago the MIL came on. Took it to my mechanic and they pulled the code P0420, which he told me pertains to "Catalytic System Not Efficient." He said that the problem might be with the front catalytic converter. Before I plunk down $600 for a new converter I just had a few questions:

1.) Could this be caused by another issue other than the catalytic converter?

2.) Is there a way to get the MIL lamp to turn off? (it's really bugging me!)

3.) My car is not due for inspection until March so I'm planning on taking it in February to have the problem repaired. My mechanic said that the car should be safe to drive and shouldn't give me any problems until then, but what do you all think? Am I REALLY okay to be driving the Altima with this problem? I'm especially concerned because my daily commute is about 60 miles (round trip) so I don't want to get stranded or damage my engine.

Again, any advice would be greatly appreciated. Thank you all and I'm sorry for coming across as such a :newbie:


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## rogoman (Dec 16, 2004)

The P0420 code could be caused by any one of the following:

• Three way catalyst (manifold)
• Exhaust pipe leak
• Intake air leaks
• Bad fuel injector(s)
• Leaking fuel injector(s)
• Dirty spark plug(s)
• Improper ignition timing


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## NALtech (Oct 30, 2009)

PO420 is catalyst efficiency below threshold bank 1. Sounds like a cat to me.......


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## 83Datsun200sx (Mar 27, 2006)

meow its a cat alright we replace thoses all day everyday.


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## Nickaltima (Jan 11, 2008)

dont put a new cat on!!!! save urself the future trouble and just put a catless header on the 2.5's cats as well as the 3.5(my cats were plugged and starting to fall apart when i put my headers on) are horrible with higher miles..do the header youll get a lil more umphhh and it will b better for ur engine in my opinion


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## 88blacktop (Oct 21, 2009)

if you have no cat you may run into problems since you have to pass emissions. you may be better off having a magnaflow high-flow cat in there.


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## Nickaltima (Jan 11, 2008)

88blacktop said:


> if you have no cat you may run into problems since you have to pass emissions. you may be better off having a magnaflow high-flow cat in there.


i deleted 2 of my cats with my headers and i have no CEL..theres tricks to that blacktop..and how do u even know he has to pass an emissions test?


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