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P0420 Diagnostic Trouble Code Discussion for April 2008

Catalyst Efficiency Below Normal (Bank 1)

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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
1999 Chevrolet Astro 4.3L MIL Lamp on VIN: 1GNEL19W7X
P0420: Catalyst System Low Efficiency (Bank 1). We have a recurring catalyst failure on this van. 5 Cats total. 1st 3 were replaced with aftermarket cats, code comes back after about 4 or 5 monitor runnings. Van drives and runs 100%. Received suggestions of possible misfire, van has been tuned and there are...
April 01, 2008
1996 Chevrolet C1500 4.3L MIL Lamp on VIN: 2GCEC19W1T
P0420: Catalyst System Low Efficiency (Bank 1). ... recurring check engine light on.We can clear the code(p0420) and some times it might stay off for a week and then some time it will come back on the next day.As mentioned the cat has been changed and o2 sensor. Both were changed due to the high mileage of ...
April 16, 2008
2000 Toyota Avalon XL 3.0L MIL Lamp on VIN: 4T1BF28B8Y
P0420: Catalyst Efficiency Below Normal (Bank 1). Before asking the customer to spend 3k on all cats and sensors, is there a way to revive a cat, or at least pinpoint which cat is causing the SES light? He is considering our estimate, but I want to be certain what he needs. Not considering an aftermarket cat,...
April 16, 2008
2002 Subaru Outback 2.5L MIL Lamp on VIN: 4S3BH665X2
P0420: Catalyst Efficiency Below Normal (Bank 1). This one has me running. Hope someone has an idea. This high mile subaru came in with a code 420 for cat. Checked sensors data to air/fuel sensor and rear o2 sensor. rear was high but varied like a front o2 and mode 6 showed fails on air/flow sensor. my solis ...
April 22, 2008
1997 BMW 528i 2.8L MIL Lamp on VIN: WB4DD6324V
P0420: catalyst efficiency below threshold bank 1. I need some help with this one. look up codes in mitchel and alldata not there . does any body have a way to check out these codes for the cats . i have been told bmw when setting these codes to replace the cats but before i replace thelm i want to confirm .an...
April 23, 2008
2002 Pontiac Firebird 3.8L MIL Lamp on VIN: 2G2FS22K52
P0420: Catalyst System Low Efficiency. ... after market cat approx. size of honey cone 4" dia. by 10". 2 weeks ago came back with 02 sensor code responsing to slow and it was so we replaced with new. After replacing with new 02 it lasted 7 days it back again this time it is cat ineffiency...
April 23, 2008
1996 GMC Sonoma SLE 4.3L MIL Lamp on VIN: 1GTCS19X2T
P0420: Catalyst System Low Efficiency. ... engine light on, code p0420, catalyst efficiency low, ...the pre and post cat o2 sensors were both ranging from below .100 to .900 rapidly very similar to the 2 front o2 sensors...removed the cat, it looked good, but was a little loose inside, rattling, re...
April 25, 2008
2003 Chevrolet Silverado 1500 5.3L Hesitation, Misfire, MIL Lamp on VIN: 2GCEK19T63
P0420: Catalyst System Low Efficiency (Bank 1). ... a po300 and 420 code. We replaced the plugs and wires. Did an injector service. We also installed a new converter assembly. We checked the misfire monitor on the scantool and all looked well. Recently the customer came back in with the same codes. We repla...
April 30, 2008