Which of the following is not used to determine emission control requirements?

• A. The engine diagnostic code list
• B. The vacuum hose routing diagram
• C. The vehicle information database
• D. The vehicle look-up tables

Answer: (C)

When figuring out what emission control requirements apply to a vehicle, you use sources that reflect the actual hardware and how it should operate. The engine diagnostic trouble code list shows which emissions-related sensors or systems are signaling faults, guiding you to test and verify the right components and their function. The vacuum hose routing diagram reveals the exact layout of the vacuum plumbing that powers several emission controls, so checking it helps identify leaks or misroutings that would impact emissions performance. The vehicle look-up tables map a vehicle’s specific hardware and testing criteria to its make, model, and year, enabling you to apply the correct procedures and limits. The vehicle information database, while useful for general reference, does not directly determine the emission control requirements, as it isn’t the source used to decide which controls a vehicle must have or how they should be tested.