When must the Tailpipe Visible Smoke inspection be conducted in relation to the tailpipe emissions test?

• A. After the tailpipe emissions test.
• B. Not required for all vehicles.
• C. May be skipped if the test passes.
• D. Before the tailpipe emissions test.

Answer: (D)

The test order requires a quick Tailpipe Visible Smoke inspection to be done before the actual tailpipe emissions test. This visual check looks for any excessive smoke from the exhaust while the engine is warmed up. If smoke is present, it signals a mechanical problem that could affect emissions results and may require repairs before you can properly measure emissions. Allowing the emissions test to proceed with smoky exhaust could yield unreliable data and waste time, so the vehicle is flagged and repairs are addressed prior to retesting.

That’s why the correct approach is to perform the visible smoke check before the tailpipe emissions test. It isn’t optional for applicable vehicles, and it isn’t appropriate to skip or perform after the test.