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P0420 Diagnostic Trouble Code Discussion for June 2013

Catalyst Efficiency Below Normal (Bank 1)

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Trouble Ticket Help Requests for DTC P0420
Help Request Posted
2003 Volkswagen Jetta GLS 2.0L Poor Idle Quality, Stall, Misfire VIN: 3VWSK69M83
P0420: cat below eff. mil flashing all times, and it runs like cat plugged up. Compression test on number 3 155 psi, I then pulled cat down and no help. Unplugged O2 both, no good mil still flashing. Then I checked compression on number 1 105 psi? Start looking at timing? Its looks...
June 28, 2013