i just got my car inspected today, and i failed the emissions part. i unplugged my battery last night cause my radio was acting strange, and when they plugged in the OBD, it read that my catalyst, evaporative system and oxygen sensor were "not ready." i had a p0420 about a month ago that i cleared by unplugging my battery overnight.

anyway, what i wanted to know is this: how long after i reset my ecu will it be "ready" and will my p0420 code show up even though my SES light is not on?

thanks for the help.

 

Drive your car 20-30 miles or so, that should reset the readiness monitors. If not, another 20 or 30 miles. Repeat as often as necessary.

 

Give it about 2 weeks worth of driving, my 01 takes about 2 weeks to set its catalyst monitoring, EVAP will be done within one hour or so worth of driving. Oxygen sensors are the same way-hour or so of driving. The emission stations do not just check for codes, but for readiness test monitors- so that no one can just clear their check engine light right before they enter the emissions station. You most likely will get the P0420 code back and will not be able to pass. There was a few threads a while back on how to eliminate that code on our Maximas.