ASE Practice Test #4

Question 1

With an electronically controlled automatic transmission, the line pressure test displays low pressure when the gearbox is idle in all gear ranges. What could be the reason?

Accepted Answer

Oil pump pressure regulator

Answer

The oil pump pressure regulator is a crucial component that controls the main line pressure within an automatic transmission. If this regulator is faulty, stuck open, or malfunctioning, it will prevent the oil pump from building and maintaining adequate hydraulic pressure across all gear ranges. This directly results in consistently low line pressure readings, impacting the transmission's ability to engage clutches and bands effectively.

Question 2

An engine starts to knock, and the sound varies with the RPM. The noise goes away when the cylinder is examined during a balance test. What is the most probable reason?

Accepted Answer

Rod bearing

Answer

A rod bearing knock is a distinct, metallic knocking sound that typically increases and decreases with engine RPM. During a cylinder balance test, disabling a specific cylinder removes the combustion load from that cylinder's connecting rod and its bearing. If the knocking sound disappears or significantly reduces when a particular cylinder is disabled, it strongly indicates a worn rod bearing on that cylinder, as the stress on it has been temporarily relieved.

Question 3

According to Technician A, when the condenser airflow is constrained, both the high and low lines are experiencing high pressure. According to technician B, low pressure on both the high and low sides is frequently a sign of low refrigerant. Who is accurate?

Accepted Answer

Both technicians

Answer

Both technicians are accurate. Technician A is correct because restricted condenser airflow prevents heat dissipation, causing refrigerant pressure to build up on both the high and low sides. Technician B is also correct; a low refrigerant charge means there isn't enough refrigerant circulating, leading to insufficient pressure on both the high and low sides of the system as the compressor struggles to move what little refrigerant is present.

Question 4

Which of these steps would you want to complete last when using a diagnostic method to check into a drivability issue?

Accepted Answer

Verify repair

Answer

In a systematic diagnostic process, verifying the repair is always the final and most critical step. After diagnosing the problem and performing the necessary repairs, it is essential to thoroughly test the vehicle to ensure the original complaint has been resolved. This confirmation ensures the effectiveness of the repair and prevents the vehicle from being returned to the customer with lingering or new issues.

Question 5

According to Technician A, the length of the spark line, which is dependent on the coil voltage and total primary circuit resistance, depends on the voltage needed to keep the spark. According to technician B, issues with the burning manifest themselves within the spark line.

Accepted Answer

Technician B

Answer

Technician B is accurate. The spark line on an ignition scope pattern represents the voltage required to sustain the spark across the spark plug gap during combustion. Any issues with the burning process, such as misfires, lean/rich conditions, or carbon fouling, will manifest as irregularities, instability, or variations in the appearance and duration of this spark line, providing valuable diagnostic information.