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P0420 Diagnostic Trouble Code Discussion for May 2005

Catalyst Efficiency Below Normal (Bank 1)

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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
2001 Pontiac Grand Prix SE 3.1L MIL Lamp on VIN: 1G2WK52J91
P0420: Catalyst System Bank 1 Low Efficiency. ... lost of power in January. Had code PO300. #2 misfire. Cleared codes and test drove o.k. Came back in 2 weeks later, wouldn't go over 25mph. Plugged up cat. Replaced cat. Test drove fine. 2 weeks later came back with check engine light on. Code 420. Cleared...
May 03, 2005
1999 Dodge Ram 1500 Laramie 3.9L Poor Fuel Economy, MIL Lamp on VIN: 1B7HC16X1X
P0420: cat conv efficiency failure. Quick qeustion for you Dodge guys. This truck runs normal,except for a rattling converter and poor fuel mileage. Question is ,can the blown up converter cause the poor fuel mileage? My guess is yes ,but would appreciate some confirmation. Thanks,Spencer.
May 04, 2005
1998 Chevrolet K1500 Cheyenne 5.0L Misfire, MIL Lamp on VIN: 1GCEK19MSW
P0420: Catalyst System Low Efficiency (Bank 1). Hi Guys, This truck came in last summer with a SES light on, another tech in our shop found a random misfire code and the customer confirmed that the truck indeed had a skip if you put it under a load for a long time(long steep grade). At that time the truck s...
May 05, 2005
1998 Lexus ES300 3.0L MIL Lamp on VIN: JT8BF28G6W
P0420: Catalyst Efficiency Below Normal (Bank 1). ... main convertor with aftermarket because of code P0420. Car came back today with same code. ( I just realized that this vehicle is California emmisions ) Fuel trims are good. Checked and read similar post from Tim Nichols. The front A/F sensors stay around ...
May 09, 2005
1998 Honda Accord LX 2.3L MIL Lamp on VIN: 1HGCG5649W
P0420: Catalyst Efficiency Below Threshold (Bank 1). P0420, Do you think converter is faulty, or could the rear HO2S be reading incorrectly? I have a friend that owns a muffler shop, he said it is rare for a Honda cat to be bad. I ran at 2000RPM in Park, monitored both HO2S with scanner. Front one toggles from a...
May 11, 2005
2001 Volkswagen Jetta Wolfsburg Edition 1.8L MIL Lamp on VIN: 3VWPD69M71
P0420: Catilyst below threshold. ... intermittened code P172 and got that resolved with your help...a new MAS did the trick. I thought we were out of the woods (we were OK for over two weeks) until the customer came back with the MIL light on again...this time code P0420. I've checked for vac...
May 17, 2005