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International Automotive Technicians Network

P0420 Diagnostic Trouble Code Discussion for June 2021

Catalyst Efficiency Below Normal (Bank 1)

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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
2009 Subaru Outback 2.5i 2.5L Poor Idle Quality, Poor Idle Quality, Poor Idle Quality VIN: 4S4BP60C09
P0420: Cat inefficiency. ... ago with a bad clutch. When it came it was dropped off, it also had a crank but no start condition. I found no spark from the coil. Replaced the coil and it started and ran fine. Proceeded to the clutch job. That went smoothly. After I finished, I noti...
June 07, 2021
2008 Chevrolet Suburban 1500 LTZ 5.3L Excessive Emissions, MIL Lamp on VIN: 3GNFK16338
P0420: Catalyst system low efficiency B1. Hey IATN community, I have a head scratcher here, or maybe I'm just making a mountain out of a molehill. So, the vehicle came to my shop after multiple repairs elsewhere that did not fix issue. Issue was CEL, intermittent misfire, and intermittent low powe...
June 12, 2021
2012 Nissan Murano LE 3.5L no power VIN: JN8AZ1MU8C
P0420: . ... drove here 20 miles but i dont see how because engine will not accelerate even in park most of the time you can put throttle on the floor and it wont rev a 1000 rpm but sometimes it will rev up but slow. did have p0420 but back pressure checks fine, i ...
June 29, 2021