Practice Test #2 1 Flashcards

A technician is diagnosing a no-start condition on a gasoline engine. The engine cranks normally but will not fire. Spark is confirmed at all cylinders. What should be tested NEXT?

Answer: Fuel pressure at the rail

With spark confirmed, the next logical step is to verify fuel delivery. Low or no fuel pressure at the rail will prevent combustion even when ignition is functioning correctly. Fuel pressure testing quickly isolates whether the fault is in the fuel system before chasing electrical components.

A customer reports that the brake pedal slowly sinks to the floor when held at a stop, but brake performance otherwise feels normal. What is the MOST likely cause?

Answer: Internal leak in the master cylinder

A pedal that sinks under steady pressure but recovers when released and re-applied is the classic symptom of an internal master cylinder bypass. The seals allow fluid to slip past under sustained load, causing the gradual loss of pedal height without any external fluid leak.

When measuring battery voltage with a digital multimeter on a fully charged 12-volt automotive battery at rest (no load), what reading should the technician expect?

Answer: 12.6 – 12.8 V

A fully charged 12-volt lead-acid battery at rest (surface charge dissipated) reads approximately 12.6 – 12.8 V. Readings below 12.4 V indicate a partially discharged battery, while 13.5 – 14.5 V is the normal charging system output seen with the engine running.

A rear-wheel drive vehicle pulls strongly to the right during braking. All four tires are properly inflated. What is the MOST likely cause?

Answer: A sticking left front brake caliper

Brake pull occurs toward the side with MORE braking force. A sticking (dragging) left front caliper can cause uneven braking, but a caliper that is seized OPEN (not applying) on the left would reduce braking on that side, pulling the vehicle toward the right where braking force is greater. This is the most common single-component cause of brake pull.

While performing a cooling system pressure test, the technician pressurizes the system to the cap rating and observes the gauge slowly dropping over five minutes with no visible external leaks. What is the MOST likely cause?

Answer: A leaking intake manifold gasket or head gasket

If pressure drops with no external leak visible, coolant is escaping internally — most commonly through a failed head gasket or intake manifold gasket into the combustion chamber or oil passages. External leaks at hoses, the radiator, or the reservoir would be visible on inspection.

A technician uses an OBD-II scanner and finds a P0420 code — Catalyst System Efficiency Below Threshold (Bank 1). What is the MOST accurate interpretation of this code?

Answer: The catalytic converter is not reducing tailpipe emissions efficiently enough

P0420 is set by the ECM when it detects that the downstream (post-cat) oxygen sensor is producing a signal too similar to the upstream sensor, indicating the catalytic converter is no longer storing and releasing oxygen efficiently. The code points to converter inefficiency, though upstream issues (exhaust leaks, rich conditions) must be ruled out before replacing the converter.