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Old 09-12-2006, 03:10 PM
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BNaylor BNaylor is offline
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Re: P0300 and P0420 On my 02 TB

The rear 02 sensor is what monitors the CAT convertor for efficiency. The P0420 DTC is being set because the PCM has detected a CAT convertor with an unacceptable amount of oxygen storage capabilities. In my experiences it is typically a flaky CAT convertor. However, Bosch aftermarket 02 sensors may give you anamolies too. You should use AC Delco 02 sensors only.

The misfires are what damages a CAT convertor. Also, a clogged CAT may cause the misfires. I would recommend getting the CAT convertor tested for efficiency.



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