CEI Evaporative Emission Control Systems

Question 1

What is the primary purpose of an evaporative emission control (EVAP) system?

Accepted Answer

To prevent fuel vapors from escaping into the atmosphere

Answer

To cool fuel before it enters the engine

Answer

To increase fuel efficiency by recirculating exhaust gases

Answer

To regulate fuel pressure in the fuel rail

Question 2

Which component in the EVAP system stores fuel vapors before they are purged into the engine?

Accepted Answer

Charcoal (activated carbon) canister

Answer

Fuel pressure regulator

Answer

PCV valve

Answer

Throttle body

Question 3

What is the function of the purge valve (purge solenoid) in an EVAP system?

Accepted Answer

It controls airflow from the canister to the intake manifold

Answer

It vents the charcoal canister to atmosphere when vapor pressure is high

Answer

It seals the fuel tank during refueling

Answer

It regulates fuel delivery pressure from the pump

Question 4

A vehicle sets a P0442 diagnostic trouble code. What does this indicate?

Accepted Answer

EVAP system small leak detected

Answer

EVAP system large leak detected

Answer

Purge valve stuck open

Answer

Charcoal canister saturated

Question 5

What does the fuel tank pressure (FTP) sensor measure in an EVAP system?

Accepted Answer

Pressure or vacuum inside the fuel tank

Answer

Fuel rail injection pressure

Answer

Barometric pressure for altitude compensation

Answer

Canister purge flow rate

Question 6

Which of the following conditions is typically required before the OBD II EVAP monitor will run?

Accepted Answer

Fuel level between 15% and 85%

Answer

Engine coolant temperature above 220°F

Answer

Vehicle speed above 60 mph for 10 minutes

Answer

Engine oil pressure below 20 psi

Question 7

What does a P0455 diagnostic trouble code indicate?

Accepted Answer

EVAP system gross (large) leak detected

Answer

EVAP system small leak detected

Answer

Vent valve circuit malfunction

Answer

Purge flow insufficient during self-test