Question about 2001 Toyota Celica
This code is generic and is the same on all vehicles.
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
Posted on Oct 03, 2010
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Posted on Jan 02, 2017
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