plugged cat

96 Silverado 305 5 spd After replacing 3 02 sensors and getting the 0420 repeatedly I finally broke down and took it to a shop I trust. He found the cat was plugged. Can a plugged cat cause 02 sensors to fail? What causes the cat to plug?

Mike

Reply to
Mike Copeland
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A PO420 doesn't indicate a failed O2 sensor(s), it signifies a loss of bank one catalyst efficiency which, being plugged makes perfect sense. Plugged cats are caused by miss-fires, over fueling, under fueling, cam timing problems, vacuum leaks, that sort of stuff.

Reply to
aarcuda69062

thanx, I had other codes telling of bad 02 sensors before but the 0420 was always there. Once I had a multiple misfire code. Once had bad heater for 02 sensor etc. Can a plugged cat take out 02 sensors? I'm just trying to get to the root cause here. The engine has 133k on it. What's the next thing to start looking at?

Reply to
Mike Copeland

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