Mixed Deck — All ASE Topics Flashcards

What is the minimum spark duration generally considered necessary for reliable combustion?

Answer: 0.5 milliseconds

A minimum of approximately 0.5 milliseconds (500 microseconds) of spark duration is generally required to reliably ignite the air-fuel mixture, especially under lean or diluted conditions.

With the battery disconnected, resistance measured between CAN High and CAN Low at DLC pins 6 and 14 on a healthy high-speed CAN bus should be about:

Answer: 60 ohms

Two 120-ohm terminating resistors in parallel produce about 60 ohms total.

To measure circuit current directly with a digital multimeter, the meter must be connected:

Answer: In series with the circuit

An ammeter must be placed in series so all circuit current passes through it.

An engine gives off heavy black exhaust smoke. What does this usually indicate?

Answer: Rich air-fuel mixture

Black smoke is carbon from unburned fuel caused by a rich mixture.

An engine coolant temperature sensor is a negative temperature coefficient (NTC) thermistor. As coolant temperature rises, its resistance:

Answer: Decreases

NTC thermistors lose resistance as temperature increases.

A secondary air injection (AIR) system pumps fresh air into the exhaust mainly during which period?

Answer: Cold start and warm-up

AIR adds oxygen during warm-up to burn HC and CO and to heat the converter faster.

Technician A says a torque converter clutch (TCC) that never releases can cause the engine to stall at stops. Technician B says a TCC that never applies will reduce fuel economy. Who is correct?

Answer: Both Technician A and B

A TCC stuck engaged stalls the engine at stops because the engine is locked to the drivetrain, and a TCC that never applies keeps the converter in slip mode reducing fuel efficiency.

Before replacing a catalytic converter for a P0420, what should a technician do first?

Answer: Fix any misfires, exhaust leaks, or fuel control problems

Root causes such as misfires, exhaust leaks, or rich conditions must be fixed, or the new converter will fail too.

A blower motor operates only on the high-speed setting. The most likely cause is:

Answer: An open blower motor resistor

High speed usually bypasses the resistor block, so an open resistor kills only the lower speeds.

What is the function of brake fluid in a hydraulic braking system?

Answer: Transfers force to braking components.

Brake fluid is a hydraulic fluid that is incompressible. When the driver presses the brake pedal, the master cylinder pressurizes the brake fluid, which then transmits this force through the brake lines to the calipers or wheel cylinders, ultimately engaging the brake pads against the rotors or drums to stop the vehicle.

In a distributor-based ignition system, what mechanism advances spark timing as engine RPM increases?

Answer: Centrifugal flyweight advance

The centrifugal advance mechanism uses flyweights inside the distributor that move outward at higher RPM, mechanically advancing ignition timing.

A P0442 code indicates which EVAP system condition?

Answer: Small leak detected (about 0.040 in.)

P0442 means the EVAP monitor found a small leak, typically about 0.040 inch.

While checking steering components, a technician observes play in an inner tie rod with the wheels on the ground. What is the correct inspection technique to confirm?

Answer: Squeeze the rack boot and feel for socket movement while a helper rocks the steering wheel

Feeling the inner tie rod socket through the boot while the steering wheel is rocked reveals looseness in the joint.

A typical acceptable maximum exhaust back pressure at 2500 RPM is about:

Answer: 1.5 psi

Most manufacturers allow about 1.5 psi or less at 2500 RPM; higher readings mean a restriction.

A technician suspects a head gasket leak into the cooling system. Which test directly detects combustion gases in the coolant?

Answer: Chemical block (combustion leak) test

A block tester draws air from the radiator through a fluid that changes color when it contacts combustion gases (CO2).

If a MAP sensor fails and reports falsely low vacuum (high load condition) to the PCM, what typically happens to ignition timing?

Answer: Timing retards to prevent knock under the falsely perceived high-load condition

The PCM interprets low manifold vacuum as high engine load and retards timing to protect against knock, resulting in reduced power and poor fuel economy.

What is the main purpose of positive caster?

Answer: To provide directional stability and steering wheel returnability

Positive caster puts the load ahead of the tire contact patch, giving straight-line stability and self-centering.

What is the purpose of a torque-to-yield (TTY) cylinder head bolt?

Answer: It is stretched into its elastic/plastic range for consistent clamping force

TTY bolts are stretched past their yield point for precise clamp load and are normally replaced, not reused.

Which sensor monitors oxygen levels in the exhaust system for optimal fuel-air mixture?

Answer: Oxygen Sensor

The oxygen sensor, also known as the O2 sensor, is located in the exhaust system and measures the amount of unburned oxygen in the exhaust gases. This data is sent to the engine control unit (ECU), which then adjusts the fuel injection to maintain an optimal air-fuel ratio for efficient combustion and reduced emissions.

What environmental regulation applies to suspension and steering?

Answer: Proper handling and disposal of fluids, refrigerants, and hazardous materials as required by EPA regulations

EPA regulations require proper handling and disposal of automotive fluids, refrigerants, and hazardous materials regardless of shop size.