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99 3.2 Code P 0420

Catalyst 1/1 efficiency below required level.

Other than not passing an emissions test, any harm or potential problems in driving with this condition?

I drove a bit with 2 bad coils and a bad intake gasket......I'm assuming this is what caused my cat problem.

Also, I recently saw but can't relocate the thread telling you which fuse in the pwr dist box to pull to clear the DTC codes....any help?
 

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vega said:
Code P 0420

Also, I recently saw but can't relocate the thread telling you which fuse in the pwr dist box to pull to clear the DTC codes....any help?
Sounds like your downstream 02 sensor is on it's way out the door.
But before you go spending crazy amounts of cash... disconnect the battery for roughly 20 minutes (this will clear out any stored codes from the PCM)... rehook everything back up. Then do what this thread tells you to do: Click Me
See if the code comes back...
 
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If in fact it is a sensor failure, it would be the UPSTREAM sensor.
 

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lbis4123 said:
isnt the downstream o2 sensor the one that monitors the cat?
You are correct. The PCM uses the downstream signal to monitor the efficiency of the cat.
 

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lbis4123 said:
so in the case of this thread it would be the downstream o2's no?
Not to say that THAT 100% would be the problem. But in most cases... I would have to say ... yes.
 

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crombie said:
Not to say that THAT 100% would be the problem. But in most cases... I would have to say ... yes.

yeah im just saying assuming that it is a sensor, it would be the downstream not the upstream like previously mentioned. is code p0430 on the driver side i assume?
 

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On a '99 it wouldn't be a bad idea to change ALL four sensors. Then no more arguing about upstream or downstream.

O2 sensors rarely go out all at once. With the thermal stresses and chemical stresses of living in the exhaust system they just get 'weak' or 'weird'.

http://www.oxygensensors.com/, there are a LOT of places that are cheaper then they are.

Be sure to rent the cut-out socket from Autozone or buy the kit from the web site for $15-. Makes the job So Much Easier.....
 

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[QUOTE='98-ESer]Be sure to rent the cut-out socket from Autozone or buy the kit from the web site for $15-. Makes the job So Much Easier.....[/QUOTE]

they sell 02 sockets at sears for like $10 i believe. they do work a whole lot better
 

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The pcm uses BOTH to monitor the cat... but its been my experience that the upstream will cause the P0420 more often than not. If in doubt... change em both or do it right and watch em with a diagnostic scan tool to see which one is screwing up.
 
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