CPT Emissions & Environmental Standards Flashcards
6 cards from real CPT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CPT Emissions & Environmental Standards flashcards as text
When an OBD-II catalyst efficiency monitor sets a P0420 code, what specific condition triggers the fault?
Answer: The downstream O2 sensor's activity level approaches the upstream sensor's activity, indicating the catalyst is no longer storing oxygen effectively
P0420 is set when the catalyst efficiency monitor detects that the downstream sensor switches as frequently as the upstream sensor, meaning the catalyst has lost its oxygen storage capacity.
What is the primary function of the Evaporative Emission Control (EVAP) system on modern US vehicles?
Answer: To capture fuel vapors from the tank and purge them into the intake for combustion rather than releasing them to the atmosphere
The EVAP system uses a charcoal canister to capture fuel vapors from the fuel tank and purges them through the intake manifold for combustion, preventing HC emissions.
A CPT technician performs an EVAP large leak test and the system cannot achieve the required vacuum. After confirming the gas cap is good, what is the most systematic next step?
Answer: Use a smoke machine to pressurize the EVAP system and visually locate the leak source
A smoke machine introduces visible smoke into the sealed EVAP system, making even small leaks visible for precise diagnosis.
Under US federal law, what is the minimum time an OBD-II system must operate (drive cycles) before an emissions-related readiness monitor is considered 'complete'?
Answer: It varies by monitor — some require one drive cycle, others require multiple specific conditions to be met
Different OBD-II monitors have different enabling conditions; some complete in one drive cycle while others (like catalyst and EVAP) require specific warm-up and drive patterns.
What exhaust gas component does a two-gas analyzer measure to evaluate combustion efficiency at idle during a basic emission inspection?
Answer: Hydrocarbons (HC) and Carbon Monoxide (CO)
A basic two-gas analyzer measures HC (unburned fuel) and CO (incomplete combustion) as the primary indicators of combustion quality during idle emission tests.
A performance modification that removes the EGR system on a street-driven vehicle in the US will most directly cause what regulatory issue?
Answer: A federal emissions tampering violation under the Clean Air Act, subject to fines, and the vehicle will fail OBD-II readiness checks for EGR monitoring
Removing an OEM emission control device violates the Clean Air Act's tampering provisions and will trigger OBD-II faults as EGR monitors fail to complete.