Po420 Error Code Question

[jseabolt]

After the distributor cap fiasco the check engine light kicked back on my father's van (98' 1500 Express) after returning from the shop. The code reader said:

 

P0420

 

Catalyst system

efficiency below

threshold bank 1

 

I cleared the code and drove the van 400 miles to the beach then the light kicked back on. Drove the van an additional 600 miles. Got home and it showed the same code again. I cleared it and drove the van back to my parent's house and the check engien light never kicked back on.

 

Most of the time if the check engine light kicks on and you clear the code, it comes back on after 30 seconds. In this case it seemed to go away for 400 miles before coming back on.

 

Is this a sign that the O2 sensor before the converter is "bad" , "going bad" or something else is causing the O2 sensor to pick up a bad signal?

 

Because of the missfiring, could unburnt fuel being dumped into the exhaust system have crapped out the O2 sensor?

 

Just wondering if it's time for a new O2 sensor. The van has 120,000 miles on it and it maybe the original sensor.

[ryank1]

It is possible that the raw fuel has damaged the convertor, but it is the o2 sensor after the cat that measures efficiency.