Emissions Control Flashcards
7 cards from real ASE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Emissions Control flashcards as text
A P0442 code indicates which EVAP system condition?
Answer: Small leak detected (about 0.040 in.)
P0442 means the EVAP monitor found a small leak, typically about 0.040 inch.
Which tool is preferred for locating a small leak in an EVAP system?
Answer: Smoke machine using nitrogen or inert gas
A smoke machine introduces visible vapor at low pressure, so leaks can be found safely.
What does the EVAP charcoal canister store?
Answer: Fuel vapors from the tank
Activated charcoal in the canister absorbs fuel vapors until they are purged into the engine.
A purge solenoid stuck open can cause which symptom right after refueling?
Answer: Hard starting and rough idle
An open purge valve pulls too much fuel vapor into the intake and makes the mixture rich, causing hard starting after a fill-up.
On many vehicles, the EVAP vent valve is normally in what state?
Answer: Open, closing only during leak testing
The vent valve normally stays open so fresh air can pass through the canister, and it closes to seal the system for leak tests.
An ORVR (Onboard Refueling Vapor Recovery) system is designed to do what?
Answer: Route refueling vapors to the charcoal canister
ORVR captures vapors displaced during refueling and sends them to the canister rather than the atmosphere.
Some EVAP leak-detection systems check for leaks while the engine is off. What do they monitor?
Answer: Natural vacuum or pressure changes as the tank cools
Engine-off natural vacuum systems watch tank pressure change as the fuel cools; a sealed system holds the vacuum.