Welcome to the new CCCUK website!
Our old website is still available but no longer open for new posts. Click here to visit it. Click here for more information.
If you're not already a member of the CCCUK, join now!

Failed CA Smog Because I reset Engine Light


New user
The guy said I failed because I reset check engine light on gmc sierra. He said go drive around 40-50 miles, then come back, should be fine. That 40-50 miles is pretty vague, does anyone know how it works? Did chevy set this? What code is the smog station checking for to allow them to know I reset the light? Any way I can tell if they will get the same error before I take it in?


Ray Quayle

CCCUK Member
The ECM checks a series of monitors, the number varies but there are usually 9 major monitors. When you reset the CE light, you clear the monitors. The smog test involves checking the ECM for NORMAL/PENDING/CONFLICT/SUSPENDED monitors. Depending on MY you can have no more than one or two monitors that aren’t NORMAL or you’ll fail. Drive cycles need to be completed before the monitors go NORMAL. This is why you were instructed to drive the 40-50 miles. Most, if not all of your monitors were PENDING when you went to test. These are the 9 major monitors:
Heated CAT
Seconday Air
Fuel System
Oxygen Sensor
Comprehensive Component Monitoring
Catalyst Efficiency