ASE A9 General Diagnosis

Question 1

A customer says their diesel pickup "runs weak and smokes." What should the technician do FIRST?

Accepted Answer

Interview the customer and verify the complaint by operating the vehicle under the same conditions

Answer

Diagnosis starts by getting the details of the complaint and verifying it. Otherwise, the technician may end up repairing a condition that is not the actual problem.

Question 2

When a scan tool retrieves a stored DTC, what does the associated freeze frame data show?

Accepted Answer

Engine operating conditions recorded at the moment the fault was stored

Answer

Freeze frame captures a snapshot of key parameters, such as rpm, load, and coolant temperature, at the time the fault was logged.

Question 3

A diesel engine emits white smoke with a sweet odor, and the coolant reservoir level keeps dropping with no external leaks. Which is the MOST likely cause?

Accepted Answer

Coolant entering the combustion chamber through a failed head gasket or cracked head

Answer

Coolant vaporizing in the cylinders produces white smoke with a sweet smell and unexplained coolant loss.

Question 4

A technician performs a crankcase pressure (blow-by) test and finds a reading well above specification at a steady rpm. What does this most likely indicate?

Accepted Answer

Excessive combustion gas passing worn piston rings and cylinder walls

Answer

High crankcase pressure means combustion gases are leaking past the rings into the crankcase, which points to worn rings or cylinders.

Question 5

A diesel engine cranks at normal speed but will not start right after the fuel filter was replaced. The new filter was installed dry. What is the MOST likely cause?

Accepted Answer

Air in the fuel system because it was not primed

Answer

A dry-installed filter leaves air in the fuel system, which prevents the injection system from building pressure and delivering fuel.

ASE A9 Practice Test

ASE A9 Practice Test

ASE A9 General Diagnosis