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My CEL has been coming on for a while, the first time I had it checked and they said it was a misfire from a cylinder, the car never seemed to perform any different so I wasn't too concerned. Since then, whenever it comes on (every other month or so) I'd just reset it with the ol' disconect the battery trick.

I decided to get the AutoZone check today and it came back with PO430 (something about the catylictic converter?) and a PO442 (which I can't even find, dude at AZ said it could be the gas cap).

Anyway, I have no mods on my car so I'm just wondering what you guys think the problem could be.
 

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p0430 is a catalytic converter below threshold.

possibly a cat that has damage or a o2 sensor that may have read something
and caused a misreading.

p0442 is a evap leak code.

may be leaking from gas cap or one of your evap valves or sensors are faulty

now if you have had a misfire present then you may have damaged the catalytic converter by haviing unburned gas in the cat. depending on how long the car has been misfiring,

i would clear the codes and then drive again and see when the light come on
at that point get it scanned and if the codes are there agian then you should take it to a repair shop. i just bought a cat for my mazda because i had a dead mis and the cat filled up with gas and melted the inside.

one of my coils went bad and my wife was driving it for a long period of time

goodluck
 

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P0420: cat system efficiency below threshold (bank1). P0430: cat system efficiency below threshold (bank2). Both put out the same diag trouble area to check.
Once these codes are detected, the ECM compares the wave form of the O2 before the cat with the wave form of the O2 sensor after the cat to determine whether or not the cat performance has deteriorated.
1. Check for gas leakage on the exhaust system. (Repair or replace)
2. Check O2 sensor/bank1,2 sensor 1 (replace)
3. Check O2 sensor/bank 1,2 sensor 2 ( replace)
4. Replace front & rear 3 way cat.
NOTE: make sure that there are no other DTC besides P0420 or P0430. If there is, then that will need to be addressed first.
 

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so i have a po430....the way im looking at it is its taking i extra air and adding fuel to cominsate for the extra air. which at the o2 sensor it is relising there is way to much unburnt gas. think its possiable that there is some intake pressure hose that is cracked letting extra air in?
 

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Hi,

I have the same P0420 and P0430 codes.

If the O2 sensors on bank 1 and 2 were also bad wouldn't they throw additional CEL codes?

Is there a different way to check the O2 sensors other than replacing them? Should I replace all 4 sensors? Can I use the universal ones all around?


Thanks.


P0420: cat system efficiency below threshold (bank1). P0430: cat system efficiency below threshold (bank2). Both put out the same diag trouble area to check.
Once these codes are detected, the ECM compares the wave form of the O2 before the cat with the wave form of the O2 sensor after the cat to determine whether or not the cat performance has deteriorated.
1. Check for gas leakage on the exhaust system. (Repair or replace)
2. Check O2 sensor/bank1,2 sensor 1 (replace)
3. Check O2 sensor/bank 1,2 sensor 2 ( replace)
4. Replace front & rear 3 way cat.
NOTE: make sure that there are no other DTC besides P0420 or P0430. If there is, then that will need to be addressed first.
 
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