Mixed Deck — All ASE4 Topics Flashcards

To isolate a parasitic draw to a specific circuit, the technician should:

Answer: Disconnect the battery and check individual fuses with a test light in series

Placing a test light or ammeter in series with each fuse while monitoring current change allows the technician to isolate the draw to a specific circuit.

When checking charging system output, the technician should perform the test with:

Answer: The engine running at 2,000 RPM with a moderate electrical load applied

Testing at 2,000 RPM with a load applied reflects real-world demand and ensures the alternator is tested under the conditions it must perform.

A technician connects a vacuum gauge and observes a steady low reading of 12 in-Hg at idle. This MOST likely indicates:

Answer: Late ignition timing

A steady but low vacuum reading at idle typically points to late ignition timing reducing combustion efficiency.

A technician measures 14.1 volts at the battery with the engine running and all accessories on. This reading indicates:

Answer: Normal charging system output

A reading of 13.5–14.7 volts at the battery with the engine running is the normal charging system output range, indicating correct alternator operation.

An engine equipped with GDI (Gasoline Direct Injection) commonly develops carbon deposits on intake valves because:

Answer: Fuel is injected directly into the cylinder and does not wash the intake valves

In GDI engines, fuel is never sprayed onto the intake valves, so oil and PCV vapors accumulate as carbon without the cleaning effect of port injection.

What is the purpose of the ECM's adaptive fuel strategy (long-term fuel trim)?

Answer: To learn and compensate for long-term changes in engine components

Long-term fuel trim allows the ECM to permanently adjust base fuel delivery to compensate for gradual changes like injector wear or sensor drift.

A P0440 series diagnostic trouble code indicates a fault in which emission control system?

Answer: Evaporative emission control (EVAP) system

P0440 through P0449 codes are assigned to the evaporative emission control system, which captures fuel tank vapors and prevents them from escaping to the atmosphere.

A throttle body has carbon deposits causing the idle to hunt. The BEST repair is to:

Answer: Clean the throttle body with approved cleaner and relearn the idle

Carbon deposits on the throttle body bore and plate can cause erratic idle, which is corrected by cleaning and performing an idle relearn.

The VVT (Variable Valve Timing) system uses which parameter to control camshaft advance?

Answer: Oil pressure delivered via ECM-controlled solenoids

VVT systems use engine oil pressure directed by ECM-controlled solenoids to hydraulically advance or retard the camshaft timing.

A scan tool shows both bank LTFT values at +18%. The MOST likely cause is:

Answer: A large vacuum leak affecting the entire engine

Equal positive fuel trims on both banks indicate a global lean condition, which points to a vacuum leak or low fuel pressure affecting the whole engine.

A technician finds fuel pressure holds for 30 seconds after the engine is shut off but then bleeds down slowly over several minutes. This MOST likely indicates:

Answer: A leaking fuel injector

Slow bleed-down of residual fuel pressure after shutdown typically indicates a leaking fuel injector allowing fuel to drip into the intake.

A MAF sensor reads 2 g/s at idle but the normal range is 3–7 g/s. The engine runs lean. This indicates the MAF sensor is:

Answer: Reading too low, causing the ECM to underdeliver fuel

A MAF reading below the actual airflow causes the ECM to calculate less fuel than needed, resulting in a lean condition.

During a fuel injector leak-down test, one injector causes a fuel pressure drop of 20 psi in 5 minutes while others show only 2–3 psi drop. This means that injector is:

Answer: Leaking internally and allowing fuel to drip into the intake

Excessive pressure drop on one injector during a static leak-down test indicates that injector is not sealing and is leaking fuel.

What information is captured in OBD II freeze frame data?

Answer: A snapshot of engine operating conditions at the moment a DTC was set

Freeze frame data stores a snapshot of key engine parameters (RPM, load, coolant temp, fuel trim, etc.) at the instant a DTC was first detected, aiding diagnosis of intermittent faults.

When diagnosing a no-start condition, the technician confirms no spark at any cylinder. The FIRST component to check is:

Answer: The crankshaft position sensor

No spark at all cylinders points to a common input signal failure; the crankshaft position sensor is the most critical common trigger.

A stuck-open EGR valve at idle will cause:

Answer: Rough idle and possible stalling

An EGR valve that stays open at idle dilutes the combustible mixture with exhaust gas, causing rough idle and potential stall.

A vacuum gauge shows a reading that slowly drops and then rises at idle. This indicates:

Answer: A restricted exhaust system

A vacuum reading that gradually drops then rises indicates a restricted exhaust is causing backpressure to build and release.

What type of information does OBD II Mode $06 provide to a technician?

Answer: On-board monitoring test results showing actual values versus pass/fail thresholds

Mode $06 reports the results of non-continuously monitored system tests, displaying actual measured values alongside minimum and maximum thresholds — useful for identifying borderline failures before a DTC sets.

What is the function of the camshaft position sensor in a modern distributorless ignition system?

Answer: It identifies cylinder #1 TDC for sequential fuel and spark delivery

The CMP sensor identifies the #1 cylinder at TDC compression so the ECM can sequence coil firing and injector timing correctly.

On a scan tool, OBD II Mode $01 PID $0C displays which parameter?

Answer: Engine RPM calculated from the crankshaft position sensor

PID $0C in Mode $01 (current data) reports calculated engine RPM derived from the crankshaft position sensor signal frequency.