ASE Practice Test (L1: Advanced Engine Performance Specialist) 1 — Questions and Answers

Question 1: The EGR (Exhaust Gas Recirculation) valve may be closed, according to a technician. A closed EGR valve would be indicated by which of the following?

Engine surge
Rough idle
Stalling
Spark knock (Correct answer)

Correct answer: Spark knock

The EGR system recirculates exhaust gases to lower combustion temperatures. If the EGR valve is closed, it prevents this cooling effect, leading to higher cylinder temperatures. These elevated temperatures can cause the air-fuel mixture to ignite prematurely, resulting in uncontrolled combustion known as spark knock or detonation.

Question 2: What is the LEAST likely reason of a gasoline tank leak:

defective seams.
corrosion.
defective tank straps. (Correct answer)
road damage.

Correct answer: defective tank straps.

Defective tank straps are designed to hold the fuel tank securely in place, not to contain fuel. While they could indirectly lead to damage if the tank becomes loose, the straps themselves do not cause a leak from the tank's sealed structure. Corrosion, defective seams, and road damage directly compromise the tank material, leading to fuel leaks.

Question 3: Blue smoke comes from the exhaust pipe of a vehicle. Technician X says that blocked cylinder head oil return passages could be the cause. Technician Y says that a stuck-open engine thermostat could be the cause. Who is right?

Both X and Y
Neither X nor Y
X only (Correct answer)
Y only

Correct answer: X only

Blue smoke from the exhaust indicates that engine oil is being burned. Blocked cylinder head oil return passages can cause oil to accumulate in the cylinder head, allowing it to seep past valve seals or guides into the combustion chamber. A stuck-open engine thermostat would cause the engine to run cold, affecting fuel economy and emissions, but not directly causing oil to burn.

Question 4: What should you do first when diagnosing an engine performance problem?

Discuss the concern with the owner of the vehicle (Correct answer)
Road test the vehicle
Check for the symptoms in the service manual
Retrieve any diagnostic trouble codes

Correct answer: Discuss the concern with the owner of the vehicle

The initial and most crucial step in diagnosing any vehicle problem is to thoroughly understand the customer's complaint. Discussing the concern with the owner provides vital information about the symptoms, when they occur, and under what conditions, which helps guide the entire diagnostic process. This ensures the technician addresses the actual problem the customer is experiencing.

Question 5: The plastic sensors on an electronically controlled EGR valve have melted. Technician X says excessive back pressure caused by a partially clogged exhaust system could be the cause. Technician Y says to always check for a restricted exhaust whenever replacing a failed EGR valve sensor. Who is right?

Both X and Y (Correct answer)
Neither X nor Y
X only
Y only

Correct answer: Both X and Y

Both technicians are correct. Excessive exhaust back pressure, often caused by a restricted exhaust system, can force hot exhaust gases back into the EGR valve, leading to overheating and melting of its plastic components. Therefore, when replacing a failed EGR valve, it is crucial to check for exhaust restrictions to prevent a recurrence of the problem, as Technician Y suggests.

Question 6: All of these reduce the life of the turbocharger, except:

exhaust system damage. (Correct answer)
lack of air cleaner maintenance.
lack of oil changes.
inadequate cooling.

Correct answer: exhaust system damage.

A turbocharger's life is primarily affected by factors related to lubrication, cooling, and the quality of air entering it. Lack of air cleaner maintenance allows debris to damage the compressor, insufficient oil changes lead to bearing wear, and inadequate cooling causes heat damage. While severe exhaust system damage could affect performance, it doesn't directly reduce the turbocharger's internal component life in the same fundamental way as issues with air, oil, or cooling.

Question 7: A vehicle is being diagnosed for poor fuel economy. Engine tests show a rich exhaust gas mixture. Technician X says that a failed oxygen (O2 ) sensor could be the cause. Technician Y says that a failed engine coolant temperature sensor could be the cause. Who is right?

Both X and Y (Correct answer)
Neither X nor Y
X only
Y only

Correct answer: Both X and Y

Both technicians are correct. A rich exhaust gas mixture indicates an excess of fuel. A failed oxygen (O2) sensor can send an inaccurate signal to the engine control module (ECM), causing it to command more fuel than necessary. Similarly, a failed engine coolant temperature sensor might incorrectly report a cold engine, prompting the ECM to enrich the fuel mixture for warm-up, even if the engine is already warm, leading to a rich condition.

Question 8: Technician X believes that paper service manuals still get used today. Technician Y believes that you should always follow recommended service procedures found in online service information. Who is correct?

Both technicians
Neither technician
Technician X
Technician Y (Correct answer)

Correct answer: Technician Y

Technician Y is correct because modern automotive repair relies heavily on up-to-date online service information. These digital resources provide the most current procedures, technical service bulletins (TSBs), and diagnostic information, which are essential for accurate and efficient repairs on contemporary vehicles. While some paper manuals may still exist, online resources are the industry standard for comprehensive and current data.

Question 9: A disconnected spark plug is interpreted by the vehicle's OBD II (On Board Diagnostic Level 2) system as a misfire that could harm the three-way catalyst. On which trip will the Malfunction Indicator Lamp (MIL) be most likely turned on by the ECM or PCM?

2nd trip
1st trip (Correct answer)
4th trip
3rd trip

Correct answer: 1st trip

A misfire condition, especially one severe enough to potentially harm the catalytic converter (a Type A or Category 1 fault), is considered critical by OBD II standards. For such severe faults, the Malfunction Indicator Lamp (MIL) is illuminated on the *first* driving cycle in which the fault is detected. This immediate alert is crucial to prevent further damage to expensive emission control components.

Question 10: The following below are true about the cylinder leakage test. Except:

air loss from the exhaust indicates a valve problem.
a gauge reading of 0 percent indicates no cylinder leakage.
air loss from the PCV valve indicates worn piston rings.
a gauge reading of 100 percent indicates no cylinder leakage. (Correct answer)

Correct answer: a gauge reading of 100 percent indicates no cylinder leakage.

A cylinder leakage test measures the percentage of air escaping from a cylinder. A gauge reading of 0 percent indicates no leakage, meaning the cylinder holds pressure perfectly. Conversely, a reading of 100 percent would indicate complete leakage, meaning all the air is escaping, which is the opposite of no leakage. Therefore, stating 100 percent indicates no leakage is incorrect.

Question 11: An engine's intake manifold is connected to a vacuum gauge. The pointer on the gauge fluctuates rapidly between 10 and 22 in.Hg when the engine is running at 2,000 rpm. The cause could be:

worn piston rings
a broken valve spring (Correct answer)
a leaking intake manifold gasket
worn piston rings

Correct answer: a broken valve spring

Rapid and wide fluctuations in vacuum gauge readings at a steady RPM (like 2,000 rpm) typically indicate an intermittent or inconsistent cylinder sealing issue. A broken valve spring would prevent the valve from closing properly and consistently, leading to a loss of compression and varying vacuum levels as the engine runs, causing the gauge needle to fluctuate erratically.

Question 12: What data do you need to know when looking for vehicle information for a given customer?

Make, model and year (Correct answer)
Vehicle VIN
Model year
Vehicle build date

Correct answer: Make, model and year

To accurately look up vehicle-specific information in service manuals or online databases, the fundamental details required are the vehicle's make, model, and year. This combination allows technicians to identify the correct specifications, procedures, and parts for a particular vehicle. While a VIN is more precise, make, model, and year are the primary initial identifiers for general information retrieval.

Question 13: Technician X says the on-board self-diagnostics test mode procedures should be conducted on a cold engine. Technician Y says many diagnostic trouble codes (DTC) will monitor items only when the engine control system is in closed loop. Who is right?

Both X and Y
Neither X nor Y
X only
Y only (Correct answer)

Correct answer: Y only

Technician Y is correct because many diagnostic trouble codes (DTCs) and self-diagnostics tests require the engine control system to be in 'closed loop' operation. Closed loop occurs when the engine reaches operating temperature and the oxygen sensors provide feedback for precise fuel control. Technician X is incorrect, as many tests specifically require a warm engine for accurate monitoring.

Question 14: Exhaust manifold testing entails all of the following. Except:

inspecting for cracks.
checking for warping with a straightedge.
cleaning all mating surfaces.
checking for restricted exhaust manifold. (Correct answer)

Correct answer: checking for restricted exhaust manifold.

Exhaust manifold testing primarily involves inspecting its physical condition for cracks, warpage, and ensuring clean mating surfaces for proper sealing. While a restricted exhaust *system* can be a diagnostic concern, the exhaust manifold itself is generally not checked for restriction in the same way a catalytic converter or muffler would be. Its primary function is to collect exhaust gases, and restriction within the manifold itself is less common than issues like cracks or warpage.

Question 15: On a vehicle that won't start, the technician discovers no spark and no injector pulses. It's possible that the cause is a failure:

crankshaft position (CKP) sensor (Correct answer)
mass airflow sensor (MAF)
fuel pump (FP) module
throttle position sensor (TPS)

Correct answer: crankshaft position (CKP) sensor

The crankshaft position (CKP) sensor is vital as it provides the ECM/PCM with engine speed and piston position information. This data is essential for timing both spark delivery and fuel injector pulses. If the CKP sensor fails, the ECM/PCM cannot accurately determine when to fire the spark plugs or open the injectors, resulting in a no-spark and no-injector-pulse condition, preventing the engine from starting.

Question 16: When using a diagnostic strategy to investigate a drivability issue, which of these actions should come last in the process?

Verify repair (Correct answer)
Verify concern
Check vehicle history
Service checks

Correct answer: Verify repair

A standard diagnostic strategy follows a logical sequence: understanding the concern, performing initial checks, diagnosing the root cause, repairing the issue, and finally, verifying that the repair has resolved the original problem. Verifying the repair is the ultimate step to ensure the customer's concern is addressed and the vehicle is functioning correctly before returning it.

Question 17: What component does the PCM or ECM monitor to assess the catalytic converter's status and, if it fails, set a DTC (Diagnostic Trouble Code)?

Front and rear O2 (oxygen) sensors (Correct answer)
Throttle position sensor
Engine coolant temperature sensor
Front and rear catalyst Temperature sensors

Correct answer: Front and rear O2 (oxygen) sensors

The PCM or ECM monitors the catalytic converter's efficiency by comparing the readings from the front (upstream) and rear (downstream) oxygen sensors. A properly functioning converter will show a significant difference in oxygen levels between the two sensors. If the rear sensor's readings mirror the front, it indicates the converter is not storing oxygen effectively, and a DTC will be set.

Question 18: Replacement of an ignition module entails all of the following. Except:

dielectric silicone is used for heat dissipation.
ignition module damage may occur without the use of dielectric silicone.
dielectric silicone is used to seal the mating surface. (Correct answer)
replacement procedures vary depending upon application.

Correct answer: dielectric silicone is used to seal the mating surface.

Dielectric silicone grease is used when replacing an ignition module primarily for heat dissipation, not for sealing. It helps transfer heat away from the module to the mounting surface (often a heat sink), preventing overheating and premature failure. Using it as a sealant is incorrect; its purpose is thermal conductivity to protect the module.

Question 19: At idle, a return-type electronic fuel injection (EFI) system produces a lot of fuel pressure. Which of these possibly be the source of the problem?

A leaking fuel pump check valve
A plugged fuel injector
High manifold vacuum
Low manifold vacuum (Correct answer)

Correct answer: Low manifold vacuum

In a return-type electronic fuel injection (EFI) system, the fuel pressure regulator is typically vacuum-referenced. High manifold vacuum (at idle) usually *reduces* fuel pressure to maintain a consistent pressure differential across the injectors. Conversely, low manifold vacuum (e.g., due to an engine problem or a disconnected vacuum line to the regulator) would cause the regulator to maintain a higher fuel pressure, leading to 'a lot of fuel pressure' at idle.

Question 20: Which of the following is an unapproved method of obtaining DTC?

Cycling the ignition switch three times over five seconds
Using a scan tool
Connecting jumper wires to the data link connector
Cycling the malfunction indicator lamp on and off (Correct answer)

Correct 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). The MIL itself is an indicator light. Approved methods include using a scan tool, which is the most common and comprehensive, or in some older vehicles, specific ignition switch cycling procedures or connecting jumper wires to the data link connector (DLC) to flash codes.

Question 21: A NO START condition is being diagnosed on a vehicle with electronic fuel injection (EFI) and distributorless ignition. Technician X says you should only use a DMM (Digital Multimeter) to check voltage values on PCM (Powertrain Control Module). Technician Y says you should use a tool to check for spark at one of the spark plugs. Who is right?

Both X and Y (Correct answer)
Neither X nor Y
X only
Y only

Correct answer: Both X and Y

Both technicians are correct. A Digital Multimeter (DMM) is the appropriate tool for accurately checking voltage values in a PCM circuit without causing damage. Additionally, when diagnosing a 'no start' condition with no spark, checking for spark at the plugs with a dedicated tool is a fundamental diagnostic step to confirm the ignition system's output. Both steps are valid and necessary in a comprehensive diagnostic approach.

Question 22: Which of the following could lead to a catalytic converter overheating?

A plugged canister purge vacuum hose
A broken air pump drive belt
A disconnected spark plug wire (Correct answer)
A stuck-closed EGR valve

Correct answer: A disconnected spark plug wire

A disconnected spark plug wire causes raw, unburnt fuel to be dumped into the exhaust system. When this unburnt fuel reaches the catalytic converter, it ignites due to the converter's high operating temperature, leading to a significant and uncontrolled temperature spike. This excessive heat can quickly damage and melt the catalyst material, causing the converter to overheat.

Question 23: Technician X believes that when the ignition coil is failing, the engine might misfire under load. Technician Y believes the pickup coil must have dielectric grease under it. Who is correct?

Both technicians (Correct answer)
Neither technician
Technician X
Technician Y

Correct answer: Both technicians

Both technicians are correct. A failing ignition coil often manifests as an engine misfire, particularly under load when higher voltage is required to jump the spark plug gap. Additionally, dielectric grease is typically applied under the pickup coil (or ignition module) in a distributor to help dissipate heat and prevent corrosion, ensuring reliable operation and proper signal generation.

Question 24: On an electronic distributor ignition (DI) system, a 12 volt test light is attached from the negative primary coil terminal to ground. While cranking the engine, the light flutters. When a spark tester is attached from the coil secondary wire to ground while revving the engine, it does not light. Which of the following is the MOST LIKELY reason for the problem?

Defective spark plug
Defective ignition coil (Correct answer)
Defective pickup coil
Defective ignition module

Correct answer: Defective ignition coil

The test light fluttering at the negative primary coil terminal indicates that the ignition module (or ECM/PCM) is correctly switching the primary circuit on and off, meaning the pickup coil and module are likely functioning. However, if there's no spark at the secondary wire despite the primary circuit working, it points directly to a failure within the ignition coil itself, preventing it from transforming the primary voltage into the high secondary voltage needed for spark.

Question 25: Any of these factors could result in engine detonation (knock). Except:

excess carbon in the combustion chambers
a stuck-closed exhaust gas recirculation (EGR) valve
a lean air fuel mixture.
retarded ignition timing. (Correct answer)

Correct answer: retarded ignition timing.

Engine detonation (knock) occurs when the air-fuel mixture ignites prematurely or spontaneously. Factors like excess carbon, a stuck-closed EGR valve (leading to higher combustion temperatures), and a lean air-fuel mixture (also increasing combustion temperatures) all contribute to detonation. Retarded ignition timing, however, delays the spark, which generally *reduces* peak combustion pressures and temperatures, thereby *preventing* detonation rather than causing it.

Question 26: After a vehicle's battery has been discharged or disconnected, which of the following could cause it to run poorly?

Learned value has been lost from ROM
PROM (programmable read only memory) failed
EPROM (erasable programmable read only memory) failed
Learned value has been lost from RAM (Correct answer)

Correct answer: Learned value has been lost from RAM

The Engine Control Module (ECM) uses volatile Random Access Memory (RAM) to store dynamic 'learned values' or adaptations that optimize engine performance. When the vehicle's battery is disconnected or discharged, RAM loses power, causing these learned values to be erased. This loss of adaptive data can lead to the engine running poorly until the ECM relearns the optimal settings through driving cycles.

Question 27: Two technicians are discussing emission diagnosis. Technician X says an ignition misfire will increase CO and HC emissions and set a DTC (Diagnostic Trouble Code). Technician Y says a misfire caused by a lean condition will increase HC and CO emissions without a DTC set. Who is right?

Both X and Y
Neither X nor Y
X only (Correct answer)
Y only

Correct answer: X only

Technician X is correct. An ignition misfire means that fuel is not burning completely, leading to increased unburnt hydrocarbons (HC) and partially burnt carbon monoxide (CO) in the exhaust. Modern vehicles are equipped with misfire detection systems that will set a Diagnostic Trouble Code (DTC) if the misfire count exceeds a calibrated threshold. Technician Y is incorrect because a misfire, even if caused by a lean condition, will typically be detected and set a DTC if severe enough, and a lean misfire often reduces CO while increasing HC.

Question 28: While the engine is running, a technician pulls the PCV valve out of the valve cover and plugs the valve opening. There are no changes in engine operation. Technician X says that the PCV valve could be stuck in the open position. Technician Y says that the hose between the intake manifold and the PCV valve could be plugged. Who is right?

Both X and Y
Neither X nor Y
X only
Y only (Correct answer)

Correct answer: Y only

Technician Y is correct. The PCV system relies on vacuum from the intake manifold to draw crankcase vapors. If the hose between the intake manifold and the PCV valve is plugged, there is no vacuum path, meaning plugging the PCV valve opening will have no effect on engine operation as no vacuum leak is being sealed. If the PCV valve were stuck open (Technician X's theory), pulling it out and plugging the opening *would* seal a significant vacuum leak and cause a noticeable change in engine operation.

Question 29: The balance of fuel injector is checked using a scan tool. What should the expected result be if the injector is working properly when following standard procedure?

ECT voltage should decrease
Engine RPM should increase with each injector that’s turned off
ECT voltage should increase
Engine RPM should decrease with each injector that’s turned off (Correct answer)

Correct answer: Engine RPM should decrease with each injector that’s turned off

When performing an injector balance test with a scan tool, the tool typically commands individual fuel injectors to temporarily shut off. If an injector is functioning correctly, turning it off will stop fuel delivery to that cylinder, causing it to cease contributing power to the engine. This reduction in power from one cylinder will result in a measurable decrease in the engine's RPM, confirming the injector's proper operation.

Question 30: A technician discovers one injector has failed but is receiving good power supply during an injector power balancing test. What should the next step be?

Continuity check between fuse and injectors
Continuity check between PCM and injector (Correct answer)
Voltage check at the ignition power feed
Voltage drop of the injector ground

Correct answer: Continuity check between PCM and injector

Since the technician has already confirmed that the failed injector is receiving a good power supply, the issue is likely on the control (ground) side of the circuit. The Powertrain Control Module (PCM) is responsible for grounding the injector to activate it. Therefore, the next logical step is to perform a continuity check between the PCM's injector driver pin and the injector's ground terminal to ensure the control wire is intact and not open or shorted.

ASE Practice Test (L1: Advanced Engine Performance Specialist) 1

The EGR (Exhaust Gas Recirculation) valve may be closed, according to a technician.
A closed EGR valve would be indicated by which of the following?