ASE L1 Practice Test

2025 Edition

ASE identifies Advanced Engine Performance Specialistas an individual service area (L1). The auto maintenance and light repair service area involves the following components:

• General Powertrain Diagnosis
• Computerized Powertrain Control Diagnosis
• Ignition Systems Diagnosis
• Fuel and Air Inductor Systems Diagnosis
• Emission Control Systems Diagnosis
• I/M Failure Diagnosis

This free sample ASE L1 Practice Test below consists of 12 questions organized within 6 sections.

Tests.com's ASE L1 Practice Test was written by Dr. John Kershaw, an 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.

For the complete practice test, flash cards, exam review and testing tips, check out Tests.com's ASE L1 Practice Exam.

General Powertrain Diagnosis

1.	An engine will not start. The technician uses a scan tool and finds DTC (Diagnostic Trouble Code) P0335 (Crankshaft Position Sensor [CKP]) stored. This vehicle has electronic ignition without a distributor. Which of the following is the MOST likely cause?
		a. Bad Engine Position Sensor ground
When the crankshaft position sensor (POS) signal is not detected by the ECM during the first few seconds of engine cranking, the ECM (engine control module) will set a code P0335. A bad (Crankshaft Position Sensor [CKP]) ground will cause the engine not to start and set this code. Incorrect answer. Please choose another answer.
		b. Defective Cam Position Sensor
When the crankshaft position sensor (POS) signal is not detected by the ECM during the first few seconds of engine cranking, the ECM (engine control module) will set a code P0335. A bad (Crankshaft Position Sensor [CKP]) ground will cause the engine not to start and set this code. Incorrect answer. Please choose another answer.
		c. Open power circuit to Ignition Coil number 1
When the crankshaft position sensor (POS) signal is not detected by the ECM during the first few seconds of engine cranking, the ECM (engine control module) will set a code P0335. A bad (Crankshaft Position Sensor [CKP]) ground will cause the engine not to start and set this code. Incorrect answer. Please choose another answer.
		d. Abnormal scope pattern
When the crankshaft position sensor (POS) signal is not detected by the ECM during the first few seconds of engine cranking, the ECM (engine control module) will set a code P0335. A bad (Crankshaft Position Sensor [CKP]) ground will cause the engine not to start and set this code. Incorrect answer. Please choose another answer.

General Powertrain Diagnosis

2.	The engine cranks but will not start. Which of the following should be checked first?
		a. Ignition circuit
On the typical NO-Start Symptom Flow Chart, the "Ignition Circuit" is listed as a priority 1 item in the order of inspection to check first. The other answers in this question could be the root cause and should be part of a sequenced diagnostic process. Incorrect answer. Please choose another answer.
		b. Ground circuit
On the typical NO-Start Symptom Flow Chart, the "Ignition Circuit" is listed as a priority 1 item in the order of inspection to check first. The other answers in this question could be the root cause and should be part of a sequenced diagnostic process. Incorrect answer. Please choose another answer.
		c. Camshaft position sensor
On the typical NO-Start Symptom Flow Chart, the "Ignition Circuit" is listed as a priority 1 item in the order of inspection to check first. The other answers in this question could be the root cause and should be part of a sequenced diagnostic process. Incorrect answer. Please choose another answer.
		d. Crankshaft position sensor
On the typical NO-Start Symptom Flow Chart, the "Ignition Circuit" is listed as a priority 1 item in the order of inspection to check first. The other answers in this question could be the root cause and should be part of a sequenced diagnostic process. Incorrect answer. Please choose another answer.

Computerized Powertrain Control Diagnosis

3.	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
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 will MOST likely set. Incorrect answer. Please choose another answer.
		b. 2nd 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 will MOST likely set. Incorrect answer. Please choose another answer.
		c. 3rd 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 will MOST likely set. Incorrect answer. Please choose another answer.
		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 will MOST likely set. Incorrect answer. Please choose another answer.

Computerized Powertrain Control Diagnosis

4.	Two technicians are discussing the ECM (engine control module) reprogramming process. Technician A says the first step in the reprogramming procedure is to determine the current software needed. Technician B says in most cases using the factory scan tool or software is needed for reprogramming. Who is right?
		a. A only
Both technicians are correct. Technician A is right because before any reprogramming takes place you must determine what software is needed and installed. Technician B is right because reprogramming is proprietary and generally requires the factory scan tool or current software with a laptop computer and adapter. Incorrect answer. Please choose another answer.
		b. B only
Both technicians are correct. Technician A is right because before any reprogramming takes place you must determine what software is needed and installed. Technician B is right because reprogramming is proprietary and generally requires the factory scan tool or current software with a laptop computer and adapter. Incorrect answer. Please choose another answer.
		c. Both A and B
Both technicians are correct. Technician A is right because before any reprogramming takes place you must determine what software is needed and installed. Technician B is right because reprogramming is proprietary and generally requires the factory scan tool or current software with a laptop computer and adapter. Incorrect answer. Please choose another answer.
		d. Neither A nor B
Both technicians are correct. Technician A is right because before any reprogramming takes place you must determine what software is needed and installed. Technician B is right because reprogramming is proprietary and generally requires the factory scan tool or current software with a laptop computer and adapter. Incorrect answer. Please choose another answer.

Ignition Systems Diagnosis

5.	A vehicle with a no-start concern has been checked with a spark checker and has no spark to the plugs. Technician A says to test for battery voltage at the ignition coil by connecting the red lead of a DMM (Digital Multimeter) to the coil negative terminal and black lead to a good ground. Technician B says with the DMM red lead on the coil negative terminal and the black lead grounded, the voltage should fluctuate while cranking the engine. Who is right?
		a. A only
Technician B is right because as the computer pulses the coil on and off the voltage reading will fluctuate. Technician A is wrong because you check for voltage at the positive terminal not the negative terminal. Incorrect answer. Please choose another answer.
		b. B only
Technician B is right because as the computer pulses the coil on and off the voltage reading will fluctuate. Technician A is wrong because you check for voltage at the positive terminal not the negative terminal. Incorrect answer. Please choose another answer.
		c. Both A and B
Technician B is right because as the computer pulses the coil on and off the voltage reading will fluctuate. Technician A is wrong because you check for voltage at the positive terminal not the negative terminal. Incorrect answer. Please choose another answer.
		d. Neither A nor B
Technician B is right because as the computer pulses the coil on and off the voltage reading will fluctuate. Technician A is wrong because you check for voltage at the positive terminal not the negative terminal. Incorrect answer. Please choose another answer.

Ignition Systems Diagnosis

6.	A vehicle has a stored and active misfire DTC (diagnostic trouble code) on a rough running engine. A broken valve spring is suspected. Which of the following tests could detect a broken valve spring?
		a. Running vacuum
The running vacuum test will show a weak or broken valve spring. Weak valve springs will produce a normal reading at idle, but as engine speed increases, the needle will fluctuate rapidly between 12 and 24 inches of Mercury. The other choices will not show a broken valve spring. Incorrect answer. Please choose another answer.
		b. Cranking vacuum
The running vacuum test will show a weak or broken valve spring. Weak valve springs will produce a normal reading at idle, but as engine speed increases, the needle will fluctuate rapidly between 12 and 24 inches of Mercury. The other choices will not show a broken valve spring. Incorrect answer. Please choose another answer.
		c. Cranking compression
The running vacuum test will show a weak or broken valve spring. Weak valve springs will produce a normal reading at idle, but as engine speed increases, the needle will fluctuate rapidly between 12 and 24 inches of Mercury. The other choices will not show a broken valve spring. Incorrect answer. Please choose another answer.
		d. Scope firing lines
The running vacuum test will show a weak or broken valve spring. Weak valve springs will produce a normal reading at idle, but as engine speed increases, the needle will fluctuate rapidly between 12 and 24 inches of Mercury. The other choices will not show a broken valve spring. Incorrect answer. Please choose another answer.

Fuel and Air Inductor Systems Diagnosis

7.	A vehicle has a stored and active misfire DTC (diagnostic trouble code) on a rough running engine. A broken valve spring is suspected. Which of the following tests could detect a broken valve spring?
		a. Running vacuum
The running vacuum test will show a weak or broken valve spring. Weak valve springs will produce a normal reading at idle, but as engine speed increases, the needle will fluctuate rapidly between 12 and 24 inches of Mercury. The other choices will not show a broken valve spring. Incorrect answer. Please choose another answer.
		b. Cranking vacuum
The running vacuum test will show a weak or broken valve spring. Weak valve springs will produce a normal reading at idle, but as engine speed increases, the needle will fluctuate rapidly between 12 and 24 inches of Mercury. The other choices will not show a broken valve spring. Incorrect answer. Please choose another answer.
		c. Cranking compression
The running vacuum test will show a weak or broken valve spring. Weak valve springs will produce a normal reading at idle, but as engine speed increases, the needle will fluctuate rapidly between 12 and 24 inches of Mercury. The other choices will not show a broken valve spring. Incorrect answer. Please choose another answer.
		d. Scope firing lines
The running vacuum test will show a weak or broken valve spring. Weak valve springs will produce a normal reading at idle, but as engine speed increases, the needle will fluctuate rapidly between 12 and 24 inches of Mercury. The other choices will not show a broken valve spring. Incorrect answer. Please choose another answer.

Fuel and Air Inductor Systems Diagnosis

8.	Two technicians are explaining emission diagnosis of the fuel system. 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 being set. Who is right?
		a. A only
Technician A is right 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.
		b. B only
Technician A is right 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.
		c. Both A and B
Technician A is right 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.
		d. Neither A nor B
Technician A is right 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.

Emission Control Systems Diagnosis

9.	A vehicle comes in with the MIL (malfunction indicator light) on with DTC (Diagnostic Trouble Code) P0456 (small leak detected in EVAP canister system). Technician A says a defective vent solenoid or a leak could be the cause. Technician B says a wrong or defective gas cap could be the cause. Who is right?
		a. A only
Both technicians are right because DTC (Diagnostic Trouble Code) P0456 (small leak detected in EVAP canister system) is caused by the following: defective vent or purge solenoid, leak in the EVAP hoses or a defective, loose or wrong gas cap. Incorrect answer. Please choose another answer.
		b. B only
Both technicians are right because DTC (Diagnostic Trouble Code) P0456 (small leak detected in EVAP canister system) is caused by the following: defective vent or purge solenoid, leak in the EVAP hoses or a defective, loose or wrong gas cap. Incorrect answer. Please choose another answer.
		c. Both A and B
Both technicians are right because DTC (Diagnostic Trouble Code) P0456 (small leak detected in EVAP canister system) is caused by the following: defective vent or purge solenoid, leak in the EVAP hoses or a defective, loose or wrong gas cap. Incorrect answer. Please choose another answer.
		d. Neither A nor B
Both technicians are right because DTC (Diagnostic Trouble Code) P0456 (small leak detected in EVAP canister system) is caused by the following: defective vent or purge solenoid, leak in the EVAP hoses or a defective, loose or wrong gas cap. Incorrect answer. Please choose another answer.

Emission Control Systems Diagnosis

10.	Which of the following would indicate a closed EGR (Exhaust Gas Recirculation) valve?
		a. Rough idle
A 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.
		b. Stalling
A 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.
		c. Spark knock
A 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.
		d. Engine surge
A 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.

I/M Failure Diagnosis

11.	Which I/M (Inspection/Maintenance) test uses a dynamometer that places a "single weight" load on the vehicle?
		a. Loaded mode test
The loaded mode test and the Acceleration Simulation Mode (ASM) requires the use of a dynamometer to place a single weight load on the vehicle, which simulates actual driving similar to the Federal test used to certify vehicles by the EPA. Incorrect answer. Please choose another answer.
		b. Acceleration Simulation Mode (ASM)
The loaded mode test and the Acceleration Simulation Mode (ASM) requires the use of a dynamometer to place a single weight load on the vehicle, which simulates actual driving similar to the Federal test used to certify vehicles by the EPA. Incorrect answer. Please choose another answer.
		c. Both A and B
The loaded mode test and the Acceleration Simulation Mode (ASM) requires the use of a dynamometer to place a single weight load on the vehicle, which simulates actual driving similar to the Federal test used to certify vehicles by the EPA. Incorrect answer. Please choose another answer.
		d. Two-Speed Idle Test
The loaded mode test and the Acceleration Simulation Mode (ASM) requires the use of a dynamometer to place a single weight load on the vehicle, which simulates actual driving similar to the Federal test used to certify vehicles by the EPA. Incorrect answer. Please choose another answer.

I/M Failure Diagnosis

12.	An engine with SFI (sequential fuel injection) has low power. The emission readings on a 5-gas analyzer suggest which of the following causes?
		a. Clogged air filter
Clogged air filter is right because the CO (Carbon Monoxide) reading is high at both 600 and 2000 RPM where at those RPM values it should have been less than 0.5% and it also increased with high RPM suggesting air starvation. HC (Hydrocarbons) is higher at 2000 RPM showing excess fuel in the system. The other readings are normal. B is wrong because a defective spark plug would have caused higher HC readings. C is wrong because a defective EGR valve would have affected NOx readings, which are normal. D is wrong because a clogged fuel filter would not show high CO. Incorrect answer. Please choose another answer.
		b. Defective spark plug
Clogged air filter is right because the CO (Carbon Monoxide) reading is high at both 600 and 2000 RPM where at those RPM values it should have been less than 0.5% and it also increased with high RPM suggesting air starvation. HC (Hydrocarbons) is higher at 2000 RPM showing excess fuel in the system. The other readings are normal. B is wrong because a defective spark plug would have caused higher HC readings. C is wrong because a defective EGR valve would have affected NOx readings, which are normal. D is wrong because a clogged fuel filter would not show high CO. Incorrect answer. Please choose another answer.
		c. Stuck Closed EGR (exhaust gas recirculation) valve
Clogged air filter is right because the CO (Carbon Monoxide) reading is high at both 600 and 2000 RPM where at those RPM values it should have been less than 0.5% and it also increased with high RPM suggesting air starvation. HC (Hydrocarbons) is higher at 2000 RPM showing excess fuel in the system. The other readings are normal. B is wrong because a defective spark plug would have caused higher HC readings. C is wrong because a defective EGR valve would have affected NOx readings, which are normal. D is wrong because a clogged fuel filter would not show high CO. Incorrect answer. Please choose another answer.
		d. Clogged fuel filter
Clogged air filter is right because the CO (Carbon Monoxide) reading is high at both 600 and 2000 RPM where at those RPM values it should have been less than 0.5% and it also increased with high RPM suggesting air starvation. HC (Hydrocarbons) is higher at 2000 RPM showing excess fuel in the system. The other readings are normal. B is wrong because a defective spark plug would have caused higher HC readings. C is wrong because a defective EGR valve would have affected NOx readings, which are normal. D is wrong because a clogged fuel filter would not show high CO. Incorrect answer. Please choose another answer.