Test Electronic Diesel Engine Diagnosis 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 Test Electronic Diesel Engine Diagnosis flashcards as text
A diesel particulate filter (DPF) will not complete a regeneration. Which condition most commonly blocks regen?
Answer: Low exhaust temperature or active fault codes preventing regen
Active fault codes or insufficient exhaust temperature will inhibit DPF regeneration from completing.
Which sensors does the ECM use to estimate DPF soot load and trigger regeneration?
Answer: DPF differential pressure and exhaust temperature sensors
Differential pressure across the DPF combined with exhaust temperature data lets the ECM estimate soot load and initiate regen.
On an SCR-equipped diesel, a DEF (urea) quality fault is set. What should be verified first?
Answer: DEF concentration, level, and the NOx/quality sensors
A DEF quality fault calls for verifying urea concentration and level along with the NOx and quality sensors before further repair.
A diesel sets a NOx sensor code intermittently. What is a common cause beyond the sensor itself?
Answer: Wiring/connector issues or exhaust leaks affecting the sensor
Intermittent NOx sensor faults are often caused by harness/connector problems or exhaust leaks rather than a failed sensor.
What does excessive crankcase pressure (blow-by) usually indicate on a diesel during diagnosis?
Answer: Worn rings, cylinders, or a restricted crankcase ventilation system
High blow-by points to worn rings or cylinders, or a plugged crankcase ventilation system allowing combustion gases past.
When performing an injector buzz/coil test electronically, what is being verified?
Answer: Electrical integrity and solenoid/coil operation of the injector
A buzz test actuates the injector solenoid to confirm the electrical circuit and coil are functioning.
A diesel runs rough with a single-cylinder misfire code. After confirming fuel supply, what targeted test isolates the fault?
Answer: Cylinder contribution test plus injector return-flow comparison
A cylinder contribution test and comparing injector return flow isolate whether the misfire is from a weak injector on that cylinder.