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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

  1. An electronic diesel sets a DTC for low boost pressure under load. Which component should be inspected first?

    Answer: Turbocharger, boost sensor, and charge-air piping for leaks

    Low boost codes are commonly caused by turbo wear, a faulty boost sensor, or leaks in the charge-air (intercooler) piping.

  2. What is the purpose of the manifold absolute pressure (MAP) sensor on a turbo diesel?

    Answer: To monitor boost/intake pressure for fueling and EGR control

    The MAP sensor reports intake manifold (boost) pressure so the ECM can manage fueling and emissions controls.

  3. A diesel exhibits white smoke at idle when cold but clears as it warms. What is the most likely benign cause?

    Answer: Incomplete combustion / unburned fuel during cold operation

    Cold-start white smoke that clears with warm-up is typically unburned fuel from incomplete combustion before the engine reaches operating temperature.

  4. When verifying a MAF sensor concern on a modern diesel, what symptom commonly results from a contaminated MAF?

    Answer: Reduced power, derate, and incorrect EGR/fueling

    A contaminated mass airflow sensor reports incorrect airflow, causing power loss, derate, and faulty EGR/fuel calculations.

  5. Which scan tool data PID best helps diagnose an EGR valve that is sticking open?

    Answer: Commanded vs. actual EGR position

    Comparing commanded EGR position to actual feedback reveals a valve that fails to follow commands, such as sticking open.

  6. A diesel goes into reduced-power (limp) mode and the lamp is on. What is the proper diagnostic approach?

    Answer: Retrieve and analyze DTCs, then test the indicated system

    Limp mode is triggered by a stored fault, so reading and analyzing DTCs before testing the specific system is the correct path.

  7. What does a slow or no glow-plug current draw on one cylinder typically indicate during testing?

    Answer: An open or high-resistance glow plug on that cylinder

    Little or no current draw on a single glow plug circuit indicates an open or high-resistance plug for that cylinder.