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P0420 Diagnostic Trouble Code Discussion for November 2009

Catalyst Efficiency Below Normal (Bank 1)

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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
2003 Toyota Corolla LE 1.8L MIL Lamp on VIN: 2T1BR32E93
P0420: Catalyst Efficiency Below Normal (Bank 1). We replaced cat convertor and rear O2 sensor for a code PO420 code returns within 2 days,we sent to dealer for reprogram but were told we need to replace the pcm for this car to fix.I can not understand how after 137000 plus miles without a code po420 that pcm...
November 09, 2009
1997 Ford Explorer Eddie Bauer 4.0L Cuts out VIN: 1FMDU34E3V
P0420: cat. eff. idles& runs good except for what sounds like backfire in intake manifold. fuel trims whent from +23 to +5 at idle after intake manifold gaskets replaced. any problems with cracks in plastic in. manifolds? still sounds like vac. leak on tipin. fuel trims +5...
November 24, 2009
2002 Chevrolet S10 2.2L MIL Lamp on VIN: 1GCCS195X2
P0420: Catalyst System Low Efficiency. Vehicle has PO420 Cat Efficency code, checked exhaust readings, all good, Oxygens sensors good, front new. Showing that light is setting at idle, all our info shows should not set untill over [...], New aftermarket converter was installed 6months ago with no p...
November 25, 2009
2001 Mazda Protege ES 2.0L Misfire, MIL Lamp on
... this job and of course it is an out of town customer leaving me no time to diagnose. Two months ago the vehicle had P0420 another tech suggest cat replacement and the 96k service, also replaced o2 sensors as well as cat. Now customer returned with P0300 an...
November 27, 2009