EGR (Exhaust Gas Recirculation) Systems Flashcards
7 cards from real Exhaust practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 EGR (Exhaust Gas Recirculation) Systems flashcards as text
Which sensor is most commonly used to directly monitor EGR flow rate?
Answer: EGR differential pressure sensor
The EGR differential pressure sensor measures the pressure drop across a restriction in the EGR circuit to calculate actual exhaust gas flow rate.
What OBD-II diagnostic trouble code most commonly indicates insufficient EGR flow?
Answer: P0401
P0401 is the standard OBD-II code for EGR Flow Insufficient Detected, meaning the PCM commanded EGR flow but measured less than expected.
Under which operating condition does the PCM typically disable EGR flow completely?
Answer: Wide-open throttle (WOT) acceleration
EGR is disabled at wide-open throttle to allow maximum airflow into the combustion chamber without dilution, ensuring full power output.
In a high-pressure EGR system, where is exhaust gas extracted from?
Answer: Upstream of the turbocharger turbine inlet
High-pressure EGR taps exhaust gas upstream of the turbocharger turbine, where exhaust pressure is highest, providing a strong pressure differential to drive recirculation.
What condition typically results from EGR cooler failure?
Answer: Coolant contamination of the intake and white smoke from exhaust
A cracked EGR cooler allows engine coolant to enter the intake manifold, producing white smoke as coolant burns in the combustion chamber and risking serious engine damage.
What is the most likely symptom of an EGR valve stuck in the closed (non-flowing) position?
Answer: Elevated NOx emissions with minimal driveability symptoms
A stuck-closed EGR valve prevents exhaust gas recirculation, causing NOx emissions to rise because combustion temperatures remain unchecked, but driveability is usually unaffected.
What material is most commonly used for EGR cooler cores due to resistance to exhaust heat and corrosion?
Answer: Stainless steel
Stainless steel is preferred for EGR cooler cores because it withstands the high temperatures and corrosive sulfur compounds present in exhaust gas better than other common metals.