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International Automotive Technicians Network

P0420 Diagnostic Trouble Code Discussion for August 2014

Catalyst Efficiency Below Normal (Bank 1)

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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
1999 Toyota Avalon XL 3.0L MIL Lamp on VIN: 4T1BF18B1X
P0420: Catalyst Efficiency Below Normal (Bank 1). I thrown the kitchen sink at this one. Vehicle won't set cat monitor and keeps setting pending code po420. Looking at repair history we done everything possible. no exhaust leaks. all other monitors set except EVAP. Need assistance or input
August 13, 2014
2001 Pontiac Aztek 3.4L MIL Lamp on VIN: 3G7DA03E01
P0420: Catalyst System Low Efficiency (Bank 1). Vehicle came in with P0420 stored. Freeze frame indicating code set at idle. Scan data shows rear o2 mimicking front o2 at idle. Engine at 2500RPM shows rear O2 oscillating between 60mv-150mv(fairly steady). My concern is the LTFT I am seeing is as high as -30...
August 18, 2014
2000 Mazda Miata 1.8L MIL Lamp on
P0420: Catalyst Efficiency Below Normal (Bank 1). This car was sent to us originaly by the local mazda dealer to put another catalyst on the car, we executed the task and put a walker ultra fit obd 2 compliant catalyst on it. check engine light came back on after two short road trips with po420. then the rear...
August 22, 2014
2001 Pontiac Grand Prix GTP 3.8L high idle VIN: 1G2WR52141
P0420: Catalyst System Bank 1 Low Efficiency. Car came n with a very high idle. 2000 rpm at idle or n gear. Customer put a cold air intake kit on vehicle, and that's when the problem started. he said there was no problems with the car before hand. So he took the cold air kit off. Still no good, high idle ...
August 27, 2014