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Old 06-08-2011, 05:08 PM   #1
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Default p0420 question

cant a damaged vacum line that runs under the */c snout cause the p0420 code to come up
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Old 06-08-2011, 05:20 PM   #2
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I don't see that causing a problem. That code is the EVAP system, and that'* a vacuum line between the fuel tank and the throttle body. At no point do the two lines share a connection.
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Old 06-08-2011, 05:29 PM   #3
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alright thank you
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Old 06-08-2011, 05:40 PM   #4
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so ive replaced both o2 sensors checked for leaks found none i replaced the cat about 2 years ago can it have failed
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Old 06-08-2011, 07:53 PM   #5
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evap doesnt have anything to do with the exhaust,

https://www.gmforum.com/showthread.p...ht=evap&page=3
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Old 06-08-2011, 08:00 PM   #6
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Old 06-08-2011, 08:21 PM   #7
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i dont see what the twc has to do with evap, so 420 would be twc not evap? i didnt look it up
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Old 06-08-2011, 08:27 PM   #8
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The service manual says check EVAP for leaks. I guess if there'* a leak it can throw the O2 sensor off.
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Old 06-08-2011, 10:56 PM   #9
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PO420 is a cat efficiency code. Could be a cat or an O2 sensor.
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Old 06-09-2011, 12:28 PM   #10
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thats what i thought, evap dont sound right

if youve replaced the cat and the o2'* you may have to find some one who has live data and check out the signal getting to the computer
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