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P0420 Diagnostic Trouble Code Discussion for July 2008

Catalyst Efficiency Below Normal (Bank 1)

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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
2000 Pontiac Grand Prix SE 3.1L MIL Lamp on VIN: 1G2WK52J13
P0420: Catalyst System Low Efficiency. Hello all I have this GP that I installed an aftermarket cat on {Walker} less than 10000 miles ago. Randomly, the MIL will come on, indicating the cat isn't doing the job.I also personally own an 02 Impala that does the same thing, and that car had a GM cat p...
July 06, 2008
2001 Pontiac Grand Prix GT 3.8L Monitor reset VIN: 1G2WP52K51
P0420: Catalyst System Bank 1 Low Efficiency. Car came in for NYS inspection. Code 420 set Graphing the downstream O2 revealed it was switching lean to rich equal to upstream O2. Replaced O2 and sensor graphed correctly. Cleared code and attempted 1st monitor reset. O2 O2 heater and EGR reset with no p...
July 07, 2008
1999 Toyota Solara SE 3.0L MIL Lamp on VIN: 2T1CF22P4X
P0420: Catalyst Efficiency Below Normal (Bank 1). ... somewhere around the rear exhaust manifold, I cannot seem to pinpoint due to all the shielding. Have smoked the exhaust system and cant find any around where the noise is. I suspect a cracked manifold. Has anyone seen this before on a v6 solara? Also setti...
July 16, 2008