When should I expect a CEL P0420 code to clear? - Nissan Forum
B14 95-99 chassis 1995-1999 Sentra and 1995-1998 200SX

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post #1 of 5 Old Jan 15th, 2010, 01:45 PM Thread Starter
Joined: Jul 2009
Location: Gaston, OR
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When should I expect a CEL P0420 code to clear?

My 97 threw a P0420 code after the holidays. I reset it once with my reader, but it reappeared the next day. Since then, I've been hands-off, and the CEL has turned off but the code remains in memory, so I can't take the car through emissions. The tags expire in two weeks, so I need to get on this.

I had assumed that the emissions system would leave the CEL on if the problem was persisting, and that the CEL turning off was an indicator that the problem was no longer active. I also assumed that after the car went through "enough" full driving cycles, the code would clear on its own, for whatever value of "enough" is required.

Is this correct, or should I manually reset the code?

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post #2 of 5 Old Jan 15th, 2010, 01:58 PM
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Yes, after a few trips, if the problem is truly gone then the light and code would disappear. Some people have reported "a few trips" as being as low as 1, but most times 3-5 20 minute drives should clear it up. If the code is still in pending mode but the CEL is on, you could have an intermittent problem. Try clearing it one more time with the scanner and drive it around for 2-3 days, if the code is still not clearing then you still have some sort of problem.
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post #3 of 5 Old Jan 15th, 2010, 02:05 PM
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Yea, if you clear the code and it continually comes back, there's an actual problem and will not go away until fixed.
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post #4 of 5 Old Jan 15th, 2010, 05:35 PM Thread Starter
Joined: Jul 2009
Location: Gaston, OR
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Yeah, that I understand. What has me asking the question is that I've never seen the CEL go out and have the code remain for as long as this one has when I didn't reset the system. I would expect a recurring problem to keep CEL lit (and no, the bulb isn't burned out).
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post #5 of 5 Old Jan 17th, 2010, 10:57 PM
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I don't know how emissions is where you live, but where I live, you can still pass emissions if you have a code in memory--just as long as the light is not on. You might ask around--that would save you a lot of stress regarding the 2-week deadline. I had a code for a cyl. 3 misfire in memory from when i replaced my clutch and somehow the wire got pulled out of the distributor. The error was in memory but the light had already gone off. They didn't care. just as long as the light wasn't on.

1997 Sentra GXE, GA16DE, M/T
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