2025 Edition

ASE A8 Practice Test

Take this ASE A8 practice test with fully explained answers and instant scoring. It is based on topics in the real exam. ASE identifies engine performance as an individual service area. The engine performance service area involves the components listed below.

The ignition system -Components that ignite the fuel and air mixture at the proper time to create maximum power and minimum emissions.
The fuel system -Components that transfer fuel from the fuel tank to the engine cylinders in the proper amounts so as to create maximum power and minimum emissions.
The exhaust system -Components that remove combustion by-products from the engine.
The emission control system -Components that reduces the amount of harmful gases emitted from the vehicle.

Tests.com's ASE Test Prep material was written by Dr. John Kershaw, ASE test prep expert: ASE test question developer; ASE Certified Master Technician; ASE Master Truck Technician; and Auto Industry Technical Instructor. Dr. Kershaw was among the first to receive ASE certification in 1972.

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General Engine Diagnosis

1.	Which of the following should be the first step in diagnosing an engine performance concern?
		a. Discussing concern with the vehicle owner
		b. Retrieve diagnostic trouble codes
		c. Check for symptoms in the on-line service manual
		d. Road test the vehicle
You need an accurate description of the customer's concern and the owner is the source. Incorrect answer. Please choose another answer.

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2.	Using a diagnostic strategy for a drivability concern, which of the following is generally the last step in that process?
		a. Checking vehicle history
		b. Verifying repair
		c. Doing service checks
		d. Verifying concern
Verifying the repair is always the last step in making sure the repair was complete. Incorrect answer. Please choose another answer.

3.	Technician A says paper service manuals are still used in today's service world. Technician B says to follow the recommended service procedures contained in the on-line service information. Who is right?
		a. A only
		b. B only
		c. Both A and B
		d. Neither A nor B
Virtually all OEM service information is accessed via the Internet. Technician A is wrong because paper service manuals are currently obsolete. Incorrect answer. Please choose another answer.

4.	When looking for specific service information, what vehicle information is needed to locate the information?
		a. Vehicle VIN
		b. Vehicle Build Date
		c. Model year
		d. Make, model and year
On almost all data services you must have the make, model and year. Incorrect answer. Please choose another answer.

Ignition Systems Diagnosis and Repair

5.	A NO START condition is being diagnosed on a vehicle with electronic fuel injection (EFI) and distributorless ignition. Technician A says you should only use a DMM (Digital Multimeter) to check voltage values on PCM (Powertrain Control Module). Technician B says you should use a tool to check for spark at one of the spark plugs. Who is right?
		a. A only
		b. B only
		c. Both A and B
		d. Neither A nor B
Both technicians are correct. Incorrect answer. Please choose another answer.

6.	What is being done in the illustration?
		a. Adjusting electronic timing
		b. Adjusting ignition timing
		c. Checking Ignition Coil polarity
		d. Checking for spark with an ST125
The illustration shows an ST125. Incorrect answer. Please choose another answer.

7.	Technician A says an engine could misfire under load if the ignition coil is tracked. Technician B says the pickup coil must dielectric grease under it. Who is right?
		a. A only
		b. B only
		c. Both A and B
		d. Neither A nor B
Both technicians are correct. Incorrect answer. Please choose another answer.

8.	A 12 volt test light is connected from the negative primary coil terminal to ground on an electronic distributor ignition (DI) system. The light flutters while cranking the engine. A spark tester does not fire when it is connected from the coil secondary wire to ground while cranking the engine. Which of the following is the MOST likely cause?
		a. Defective ignition coil
		b. Defective pickup coil
		c. Defective ignition module
		d. Defective spark plug
The test light going off and on indicates that the ignition coil triggering device is working but the failure of a spark indicates a coil failure. Incorrect answer. Please choose another answer.

Fuel, Air Induction and Exhaust Systems Diagnosis and Repair

9.	Two technicians are discussing emission diagnosis. Technician A says an ignition misfire will increase CO and HC emissions and set a DTC (Diagnostic Trouble Code). Technician B says a misfire caused by a lean condition will increase HC and CO emissions without a DTC set. Who is right?
		a. A only
		b. B only
		c. Both A and B
		d. Neither A nor B
Technician A is correct because all misfires set a Specific DTC and will increase HC and CO. Technician B is wrong because a lean misfire also sets a DTC and will not increase HC and CO. Incorrect answer. Please choose another answer.

10.	A scan tool is being used to check fuel injector balance. Based on service manual procedure, what is the expected result if the injector is functioning properly?
		a. Engine RPM should increase as each injector is turned off
		b. Engine RPM should decrease as each injector is turned off
		c. ECT (Engine Coolant Temperature) Voltage should decrease
		d. ECT (Engine Coolant Temperature) Voltage should increase
Engine RPM will decrease as each injector is turned off unless there is a fault in the cylinder. There will be no change in coolant temperature. Incorrect answer. Please choose another answer.

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11.	During an injector power balance test, a technician finds one injector has failed but is receiving a good power supply. What should be done next?
		a. Voltage drop of the injector ground
		b. Voltage check at the ignition power feed
		c. Continuity check between PCM and injector
		d. Continuity check between fuse and injectors
The recommendation by most ESM is to do a continuity check between the PCM and injectors, when adequate power is available to the injector. Incorrect answer. Please choose another answer.

12.	Which of the following could cause a vehicle to run poorly after the battery was discharged or disconnected?
		a. PROM (programmable read only memory) failed
		b. EPROM (erasable programmable read only memory) failed
		c. Learned value has been lost from RAM
		d. Learned value has been lost from ROM
If battery power is lost the learned value from the RAM may be lost. RAM data is electronically retained which means that it is always to some extent volatile; that is, data storage could be described as temporary - if the circuit is opened, RAM data is lost. It should be noted that most PCMs use only fully volatile RAM. In other words, when the ignition circuit is opened all RAM data is dumped. A second type of RAM is used in some PCMs. This is non-volatile RAM (NV-RAM) (or KAM-Keep alive memory) in which data is retained until either the battery is disconnected or the PCM is reset, usually by depressing a computer reset button, which temporarily opens the circuit. Codes and failure strategy (action sequence) would be written to NV-RAM and retained until reset. Incorrect answer. Please choose another answer.

Emission Control Systems Diagnosis and Repair

13.	Technician A says a crushed PCV hose affects idle on some engines and also can cause an oil leak. Technician B says when checking crankcase pressure at 2500 RPM, the PCV system should show a slight pressure in the crankcase at idle. Who is right?
		a. A only
		b. B only
		c. Both A and B
		d. Neither A nor B
Technician A is correct because on many engines the PCV provides a portion of the idle air and if it is restricted it creates positive crankcase pressure which will push the engine oil out of the engine. Technician B is wrong because the PCV system should create a slight vacuum in the crankcase at 2500 RPM. Incorrect answer. Please choose another answer.

14.	Technician A says if the PCV valve is clogged, the engine could have a rough idle. Technician B says if the PCV valve rattles, then it does not need to be replaced. Who is right?
		a. A only
		b. B only
		c. Both A and B
		d. Neither A nor B
Technician A is correct because a portion of the idle air is furnished by the PCV system. Technician B is wrong because the rattle alone does not dictate proper operation. Incorrect answer. Please choose another answer.

15.	A technician suspects the EGR (Exhaust Gas Recirculation) valve is closed. Which of the following would indicate a closed EGR valve?
		a. Rough idle
		b. Stalling
		c. Spark knock
		d. Engine surge
Spark knock is a symptom of an EGR valve that is always closed. The other choices are wrong because they are symptoms of an EGR valve that is always open. Incorrect answer. Please choose another answer.

16.	The plastic sensors on an electronically controlled EGR valve have melted. Technician A says excessive back pressure caused by a partially clogged exhaust system could be the cause. Technician B says to always check for a restricted exhaust whenever replacing a failed EGR valve sensor. Who is right?
		a. A only
		b. B only
		c. Both A and B
		d. Neither A nor B
Both technicians are correct. Incorrect answer. Please choose another answer.

Computerized Engine Controls Diagnosis and Repair

17.	This question has the word EXCEPT. For this question, look for the choice that could NOT meet the described situation. Read the entire question carefully before choosing your answer. Long-term fuel trim is a Self-Learned value. Disconnecting the MAF sensor or using a scan tool can clear a learned value. Many fuel system and emission components have a direct effect on the air/fuel mixture ratio. Self-Learning Control should be cleared each time any of these components have been replaced or repaired, EXCEPT:
		a. MAF (Mass Air Flow) sensor
		b. Oxygen sensor
		c. PCV (positive crankcase ventilator) valve
		d. Fuel injectors
PCV valve is the exception because it has a very indirect effect on the air/fuel mixture ratio and is not an electronic component. Incorrect answer. Please choose another answer.

18.	The OBD II (On Board Diagnostic Level 2) system on a vehicle interprets a disconnected spark plug as a misfire that could damage the three-way catalyst. On which trip will the ECM or PCM MOST likely turn on the Malfunction Indicator Lamp (MIL)?
		a. 1st trip
		b. 2nd trip
		c. 3rd trip
		d. 4th trip
It is most likely that on the first trip a misfire condition can occur that can damage the three way catalyst (TWC) due to overheating. Specific on board diagnostic items will cause the ECM to light up or blink the MIL, and store DTC and Freeze Frame data, even in the 1st trip; e.g., Misfire (Possible three way catalyst damage) - DTC: P0300 -P0306 is being detected. Incorrect answer. Please choose another answer.

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19.	Technician A says the on-board self-diagnostics test mode procedures should be conducted on a cold engine. Technician B says many diagnostic trouble codes (DTC) will monitor items only when the engine control system is in closed loop. Who is right?
		a. A only
		b. B only
		c. Both A and B
		d. Neither A nor B
Technician B is correct because many diagnostic trouble codes (DTC) will monitor items only when the engine control system is in closed loop. Closed loop operation requires the engine to reach a certain operating temperature before it can be entered. Technician A is wrong because the on-board self-diagnostics test mode procedures should be conducted on a warm engine (NOT a COLD engine as stated in the question) that is in closed loop because many DTCs only monitor in closed loop. Incorrect answer. Please choose another answer.

20.	What component does the PCM or ECM monitor to determine the condition of the catalytic converter and will set a DTC (Diagnostic Trouble Code) if it fails?
		a. Throttle position sensor
		b. Engine coolant temperature sensor
		c. Front and rear catalyst Temperature sensors
		d. Front and rear O2 (oxygen) sensors
On vehicles equipped with OBD II, use of two oxygen sensors is required to monitor catalytic converter efficiency. The front oxygen sensor is located before the catalytic converter (upstream) and the rear oxygen sensor is located after the converter (downstream). During closed loop fuel control, the ECM compares the signals from the two oxygen sensors. One important point to remember is that a rear O2 sensor is used only for diagnostics. It usually has no influence on engine operation or driveability. Incorrect answer. Please choose another answer.

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Among first ASE Certified in 1972

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