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p0420 question

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Old 06-08-2011, 04:08 PM
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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, 04:20 PM
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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, 04:29 PM
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alright thank you
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Old 06-08-2011, 04:40 PM
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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, 06:53 PM
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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, 07:00 PM
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But the P0420 code does. https://www.gmforum.com/showthread.p...86#post1390979
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Old 06-08-2011, 07:21 PM
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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, 07:27 PM
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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, 09:56 PM
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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, 11:28 AM
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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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