Originally posted by GregH:
It does work, but it is just postponing the inevitable. o2 switch ratios are easy to measure - it's hard to believe that a pcm update will rejuvenate a catalytic convertor.



The PCM re-flash doesn't do a thing to the catalytic converters; from what I read in the TSB, it just changes the logic that interprets the O2 sensor output to determine whether the cats are performing acceptably.

I interpret that to mean the "old" logic was prone to spurious alarms whereas the revised logic is not. That's different from simply "raising the alarm threshold" or lowering the bar for a successful diagnostic. To me, this corrects an error in the logic.

If my catalytic converters are indeed going downhill, that certainly hasn't manifested itself in any of the state emissions test results for the car. Not only are the numbers (CO, NOx, HC's, etc.) well below the allowable thresholds (and not trending upwards through the years), but also consider that in order to pass, all onboard emissions tests must be complete and passed, including the cat efficiency test. And no, I haven't had the PCM re-flash performed. The P0420's I get are, as far as I can tell, spurious.

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