Exhaust Emissions & Catalytic Converters Flashcards
6 cards from real Exhaust practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
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What is the primary function of a catalytic converter in a vehicle's exhaust system?
Answer: To reduce harmful exhaust emissions
A catalytic converter uses chemical reactions to convert harmful pollutants like CO, NOx, and hydrocarbons into less harmful substances.
Which of the following gases is NOT typically targeted for reduction by a three-way catalytic converter?
Answer: Carbon dioxide (CO2)
Three-way catalytic converters target CO, NOx, and unburned hydrocarbons; CO2 is a byproduct of complete combustion and is not reduced by the converter.
What precious metal is most commonly used in catalytic converters to facilitate oxidation reactions?
Answer: Platinum
Platinum is the primary catalyst used in oxidation reactions within catalytic converters, alongside palladium and rhodium.
The OBD-II system monitors catalytic converter efficiency primarily using which sensor?
Answer: Downstream oxygen sensor
The downstream (post-cat) oxygen sensor compares its readings to the upstream sensor to determine if the catalytic converter is functioning efficiently.
Which emission standard, introduced federally in the US, requires vehicles to meet strict NOx and particulate limits?
Answer: Tier 3
The EPA's Tier 3 emission standards, phased in from 2017, require significant reductions in NOx and particulate matter from new vehicles sold in the US.
What condition is indicated when the Check Engine light triggers code P0420?
Answer: Catalytic converter efficiency below threshold
OBD-II code P0420 indicates that the catalytic converter's efficiency has dropped below the acceptable threshold monitored by Bank 1.