Which crankcase emission controls are visually inspected on diesel vehicles?

• A. Positive Crankcase Ventilation (PCV); Crankcase Depression Regulator (CDR); Crankcase Ventilation (CCV)
• B. PCV; CCV only
• C. PCV; CDR only
• D. CCV; CDR only

Answer: (A)

Diesel crankcase emission control relies on venting crankcase gases in a controlled way so they don’t escape to the atmosphere. Visually inspecting these controls means looking for the physical components and their condition: the PCV valve and its hoses, the CCV system and its lines, and the Crankcase Depression Regulator that sets the crankcase vacuum. All three can be seen and checked during a visual inspection, so the complete, correct set to inspect is PCV, CCV, and CDR. If a component is missing, damaged, or disconnected, it can compromise emissions control. The other options omit at least one of these components, so they don’t reflect everything that can be visually checked.