I have a 2002 Toyota Sienna XLE.
Ever since I owned the van it has had a P0420 Catalyst efficieny below threshold, clearing the codes it always comes back after about 35 miles, I live in a state with no inspections so I just leave it since it will cause no harm since the sensor in question is not a Air/Fuel sensor.
Anyways a little over a week ago the van had a EVAP code so I cleaned the o-ring of the gas cap, put it back on tight cleared the codes and it didn’t come back but after 35 miles the P0420 came back as usual. Then a few days for some odd reason the check engine light turned off on its own.
I hook up the OBDII scanner and P0420 is still stored as an ACTIVE code so the check engine light should be on because it is not a history or pending code. When the key is to the on-position the Check engine light does light up so the bulb is fine.
I am just confused on what is going on here, I am going to take it for a good long drive tomorrow to see if the light comes back on but I don’t know if this is a Toyota thing, the van runs and drives fine no issues. I don’t want to clear the P0420 code currently stored as ACTIVE because I don’t know what is going on since the check engine light is off when it should be on.
Any ideas on why it is doing this? is this common for Toyota’s of this age to do this? This is the first Toyota I have owned so I am not really too familiar with everything on it yet.
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