# Throwing ECU code 0420



## Marvin (Oct 16, 2002)

I read in the ECM what the code stood for, but I have no clue what the problem is. Can anyone put this into English for me?


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## Marvin (Oct 16, 2002)

anyone?


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## fugiot (Jun 27, 2003)

Your car just wants to smoke a bowl :cheers:


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## jayman9207 (Nov 20, 2002)

Give me your email address and I will send you the info via PDF.


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## lshadoff (Nov 26, 2002)

Code 0402 is the Three Way Catalyst Function. It is detected when:
[Edit: 0420, made a typo]

The converter does not function correctly
The converter does not have enough oxygen storage capacity.

Possible causes are:
Bad converter
Clogged exhaust system (dents)
Exhaust leak
Bad injector(s)

Lew


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## altima25s (Feb 26, 2003)

lshadoff said:


> Code 0402 is the Three Way Catalyst Function. It is detected when:
> 
> The converter does not function correctly
> The converter does not have enough oxygen storage capacity.
> ...




ya car is telling you to chill out and smoke a blunt lol


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## altima25s (Feb 26, 2003)

altima25s said:


> ya car is telling you to chill out and smoke a blunt lol




nah honestly though...code 420 is frion...the air conditioning, i believe


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## jayman9207 (Nov 20, 2002)

You can download the error code information from the ESM here: www.jay-man.net/altimas.net/esm/P0420.pdf.


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## Ruben (Oct 15, 2002)

lshadoff said:


> Code 0402 is the Three Way Catalyst Function. It is detected when:
> [Edit: 0420, made a typo]
> 
> The converter does not function correctly
> ...


All the above is true... and a bad wiring job on your casper sim can cause that.


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## KA24Tech (Feb 2, 2004)

The 0420 code is the Catalyst Efficiency Below Threshhold usually triggered when you have a highflow exhaust, removed the cat, and/or have a bad O2 sensor. What it means is that the O2 sensor at the rear is showing above normal levels of hydrocarbons and sends this back to the ECU in a higher voltage. Sometimes I have seen this when the car has an aftermarket exhaust and the person does alot of highway cruising. The extended cruise allows the O2 to have small and slow fluctuations and the ECU thinks something is wrong, then turns on the Service Light. I would take it into the dealer and they can determine if you have a bad O2 or something which is contributing to the 0420 code.

Troy


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## Marvin (Oct 16, 2002)

Well, I have the pre-cat removed with the HS header and I have an o2 sim that needs to be installed. The cat had been gone for about 3 weeks before that code finally showed up. The 0037 code for an error with the second o2 sensor went away when this one popped up.


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## Ruben (Oct 15, 2002)

When you install the sim, that will go away. Strangley enough, I have both o2 sensors in my header before the secondary cat, with my new hotshot, and I haven't thrown a code in over 1000 miles... knock on wood.


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## ALTYHOLIC (Oct 19, 2002)

Altim8GA said:


> Well, I have the pre-cat removed with the HS header and I have an o2 sim that needs to be installed. The cat had been gone for about 3 weeks before that code finally showed up. The 0037 code for an error with the second o2 sensor went away when this one popped up.


Where are you at with this problem, Mark?


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