California Smog Check Inspector Practice Test

Which monitor is allowed to be incomplete for 1996 through 1999 gasoline powered vehicles?

1. Oxygen sensor monitor

2. Evaporative system monitor

3. Mass airflow monitor

4. Fuel system monitor

The correct answer is: Evaporative system monitor

For gasoline-powered vehicles manufactured between 1996 and 1999, the evaporative system monitor is the only monitor that is permitted to be incomplete during a smog check. Federal regulations establish that certain readiness monitors must be set to "ready" for the vehicle to pass emissions testing. However, for that specific model year range, the incomplete status of the evaporative system monitor does not result in an automatic failure. This allowance is significant because the evaporative system monitor checks for leaks and proper functioning of the vehicle's vapor recovery systems, which are essential for controlling emissions. Due to the complexity of the system and various factors affecting its readiness—such as temperature, fuel level, and driving conditions—some vehicles may have difficulty completing this monitor in certain circumstances. In contrast, other monitors such as the oxygen sensor, mass airflow sensor, and fuel system monitors generally need to be complete for the vehicle to pass the smog check. The requirement for these monitors stems from their critical role in managing fuel efficiency and emissions, making it essential for them to demonstrate proper functionality.