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Old 02-15-2009, 10:41 PM   #1
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I have a code po420 on my 01 bonneville,check eng light came on,seems to be low on power but not running rough,anyone else have this and can lead me to the problem thanks ahead
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Old 02-15-2009, 10:44 PM   #2
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Check this out. It will help you figure out where you need to look OBD-II Trouble Code: P0420 Catalyst System Efficiency Below Threshold (Bank 1)
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Old 02-15-2009, 10:44 PM   #3
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420 catalyst system low efficiency

Check your rear O2 sensor
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Old 02-15-2009, 11:20 PM   #4
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would the sensor produce low power,I was thinking a bad cat since it has loss of power also
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Old 02-15-2009, 11:29 PM   #5
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If the sensor is going bad it will trip a code. Also, if the cat is going bad, it will trip a code.
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Old 03-18-2009, 01:06 PM   #6
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so is it the first 02 senor before the convertor the the one after the convertor if you got this code?
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Old 03-24-2009, 02:00 PM   #7
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How can a sensor be the first check, when that is telling the computer there isn't enough of a difference from what the front and back sensors are reading?

Did a quick search and came up with the FSM info on this code.
http://www.gearchatter.com/viewtopic...ighlight=p0420

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Old 04-05-2009, 03:51 AM   #8
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With the lack of power it is most likely the converter. Unbolt the front of the converter so you have open exhaust and test drive to see if the power is restored.
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Old 04-06-2009, 05:03 PM   #9
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this check engine light is making me mad
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Old 04-06-2009, 06:00 PM   #10
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Quote:
Originally Posted by chubbyboy88 View Post
so is it the first 02 senor before the convertor the the one after the convertor if you got this code?
Rear sensor...after the cat.
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