What is the correct procedure for functional tests during a Smog Check?

• A. Follow the procedures specified by the vehicle's manufacturer to perform required Smog Check functional tests.
• B. Use a standard one-size-fits-all procedure.
• C. Skip functional tests for older vehicles.
• D. Perform only the basic tailpipe test.

Answer: (A)

Functional tests must be performed following the vehicle manufacturer's procedures. These procedures specify the exact diagnostic modes, sequence, and tool connections needed for each system, so the test reflects how the car is designed to operate and ensures accurate results. Regulatory standards require verifying that the appropriate onboard monitors are ready and that fault codes are read and handled correctly, which manufacturer guidelines help ensure. Using a generic, one-size-fits-all approach can miss model-specific steps or safety checks, and skipping functional tests for older vehicles would neglect required verification. A tailpipe test alone only shows emissions at a moment in time and does not confirm that the emission-control systems and diagnostic monitors are functioning properly. Following the manufacturer’s procedure ensures a valid, compliant functional test.