Practice Test Flashcards

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?

Answer: Oil pump pressure regulator

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.

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?

Answer: Rod bearing

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.

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?

Answer: Both technicians

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.

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

Answer: Verify repair

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.

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.

Answer: Technician B

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.

Refrigerant must be added to: in order to charge the air conditioning system while it is operating.

Answer: the low side

When charging an air conditioning system with the engine operating, refrigerant must always be added to the low-pressure (suction) side. This allows the compressor to draw in the refrigerant as a vapor, preventing liquid refrigerant from entering the compressor. Introducing liquid refrigerant directly into the compressor can cause severe damage due to hydro-lock, as the compressor is designed to pump gas, not incompressible liquid.

At higher speeds than specified, shifting in an automatic transaxle starts to happen. ALL OF THESE, WITH THE EXCEPTION OF:

Answer: Weak governor spring tension

The governor in an automatic transaxle uses centrifugal force to determine shift points based on vehicle speed. If the governor spring tension is *weak*, the governor weights would move outward at *lower* speeds than intended, causing the transmission to shift *earlier* than specified. Conversely, excessive governor spring tension, worn weights, or a sticking governor valve would lead to delayed shifts, occurring at higher speeds.

The heater is not blowing warm air, according to a consumer who enters the store. When activated, it blows frigid air. Although the temperature never rises, all fan speed settings are functional. Which of the subsequent problems is most likely to be at fault?

Answer: A restricted heater core

If the heater is blowing cold air despite the fan working and the temperature selector set to warm, it indicates that hot engine coolant is not effectively flowing through or transferring heat within the heater core. A restricted heater core prevents proper circulation of hot coolant, thereby preventing it from heating the air that passes over its fins, resulting in only cold air being delivered to the cabin.

Which of these methods is not permitted for obtaining DTC?

Answer: Cycling the malfunction indicator lamp on and off

Cycling the malfunction indicator lamp (MIL) on and off is not a recognized method for retrieving Diagnostic Trouble Codes (DTCs). Standard methods include using a scan tool for comprehensive diagnostics, or in some older vehicles, specific procedures like connecting jumper wires to the data link connector or cycling the ignition switch a set number of times to flash codes on the MIL.

What is the MOST likely explanation if the transmission can change into two gears at once?

Answer: Faulty interlock

The interlock mechanism in a manual transmission is specifically designed to prevent the simultaneous engagement of two gears. If this mechanism fails or becomes faulty, it can allow the shift forks to move into positions where two different gears are engaged at the same time. This condition can cause the transmission to lock up, make shifting impossible, or lead to severe internal damage.

You are running a cylinder compression test and got a zero compression reading plus severe engine blowby. This indicates which of the following?

Answer: A hole in a piston

A hole in a piston creates a direct pathway for combustion gases to escape into the crankcase, causing severe engine blowby. Simultaneously, this breach prevents the cylinder from holding any pressure during the compression stroke, resulting in a zero compression reading. This specific combination of symptoms points definitively to a catastrophic failure of the piston itself.