If the P 0420 does not disappear within a week of normal start-stop-start-go driving, THEN consider having a dealer (or AutoZone) clear the SES........ or go out in the boonies and literally run the dog-snot out of the car. You won't hurt it. The Northstar is a very, very happy engine up around 5500 rpm.
IF a fault is sensed, a code sets (and maybe the SES if it's an emission code). The code remains Current for three start-run cycles during which the fault does not occur. Then the code goes to History and the light should extinguish. The code will remain as History for at least 30 start-run cycles during which the fault does not again set, when the code self-clears.
IF a fault is sensed, a code sets (and maybe the SES if it's an emission code). The code remains Current for three start-run cycles during which the fault does not occur. Then the code goes to History and the light should extinguish. The code will remain as History for at least 30 start-run cycles during which the fault does not again set, when the code self-clears.
