When should I expect a CEL P0420 code to clear?
My 97 threw a P0420 code after the holidays. I reset it once with my reader, but it reappeared the next day. Since then, I've been hands-off, and the CEL has turned off but the code remains in memory, so I can't take the car through emissions. The tags expire in two weeks, so I need to get on this.
I had assumed that the emissions system would leave the CEL on if the problem was persisting, and that the CEL turning off was an indicator that the problem was no longer active. I also assumed that after the car went through "enough" full driving cycles, the code would clear on its own, for whatever value of "enough" is required.
Is this correct, or should I manually reset the code?