trouble code P0420 "catalyst system efficiency below threshold", Ican guess but rather know exactly the meaning can you help?
Jan 19, 2011 at 3:17 AM
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JACOBANDNICKOLAS
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Basically that is saying the catalytic converter isn't working. However, that same code can be set by a bad O2 sensor. Check to make sure the sensor (using a live data scanner) is staying witin .25v and .35v. If it is outside that, the sensor is bad.