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P0420 Diagnostic Trouble Code Discussion for August 2010

Catalyst Efficiency Below Normal (Bank 1)

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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
2004 Cadillac Escalade 6.0L Poor Idle Quality, Misfire, MIL Lamp on VIN: 1GYEK63N74
P0420: Catalyst System Low Efficiency (Bank 1). ... light on check codes code p0300 and p0420. Check misfire data #2 cylinder had multiple misfires counts 829. some on other cylinders too but number 2 the worst. Check plugs and wires they had been changed. Check fuel pressure ok 55psi. Let vehicle set overn...
August 26, 2010
2000 Chevrolet Express 1500 4.3L MIL Lamp on VIN: 1GBFG15W6Y
P0420: Catalyst System Low Efficiency (Bank 1). hello fellow technicians. truck came in for misfire. found 4 codes listed. also i dont understand why i have a a.i.r code, this truck has no a.i.r system. atleast no relay, fuse or pump. well anyways wires were arcing and plugs were .030 worn over gap. replace...
August 30, 2010
2005 Ford F-350 Super Duty XL 5.4L Hesitation, Misfire, MIL Lamp on VIN: 1FTWW31545
P0420: Bank 1 Cat Efficiency Low. This truck intermittently falls on its face while accelerating, its happening more and more. Both 02 sensors stay at around .95V and short term fuel trim is -20%. Map sensor voltage is at 4.99V. Its like this thing cannot get enough air. I did find a TSB #07M0...
August 31, 2010