I have a 1999 Suburban with 160,000 miles on it. It recently needed a Calif smog check. I took it in to a test station and it passed with flying colors except it showed a malfunction in the EGR system. The MIL was NOT on. I drove the vehicle home and removed the electrically operated EGR. It had a stuck valve. I cleaned the carbon off and the valve now moved freely. I reinstalled it and connected my Actron scan tool (which I didn't do before taking it for the smog test). The scan tool read P0404 (EGR system). I cleared the old code from the vehicle. No new code appeared and I drove for about 25 miles. Still no new codes. I then went back for a retest. When the tech plugged in his machine it showed EGR was OK but it said three systems were NOT ready for testing They were "catalyst", "Secondary Air System" and "Evaporitive System". The tech suggested that I drive the vehicle for 50 to a 100 miles to reset the three things. I drove for over a 100 miles during the next week and went to the smog test again. It still showed the three systems not ready for testing. I drove for another 120 miles over another week and went in again yesterday. Same three systems are still not ready for testing. What can I do? I have no clue why the systems originally tested OK the first time and now they show "Not Ready". The battery has NOT been disconnected and simply clearing old trouble codes with my scan tool should not cause systems to need resetting. I understand what the three systems are but why won't they reset?

 

If you used your Actron to clear the code it also resets all the drive monitors...its not just the drive time its the drive cycles, meaning you need to stop and go some and key off on and start cycles.

 

evap monitor won't run will the fuel tank over 3/4 or under 1/4 full.



You will have to search out the driving conditons required to complete the monitors. Then drive to enable those conditons.

 

Thanks very much for the advice. It seems to me that after driving over 240 miles over several weeks with numerous starts and stops and short and longer (40 mile) trips that the three ststems should be reset by now. Does anyone know what GM says that the requirments are? Maybe I have to go a certain distance in reverse!!!