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98 accord 4cylvtec at and getting p0420 code if reset fuse will stay off for a week Will only come back in you run the car hard ie shift to third on highway and hit 6000rpm any thoughts on fault?

Answer

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Wiki User
11/06/2007

P0420 = Catalyst System Efficiency Below ThresholdCatalyst System Efficiency Below Threshold. This means that the secondary O2 sensor detects that the catalytic converter isn't working as efficiently as it should. This engine code can be triggered by any one of the following:

1.) The catalyst in the catalytic converter is cracked, clogged, or otherwise damaged.

2.) The secondary O2 sensor is malfunctioning.

3.) There is an exhaust leak.

4.) The computer unit is faulty