Michigan Automotive Diagnostics Exam
question with correct answers
(100% verified answers) plus rationales Q &A
2026 INSTANT DOWNLOAD PDF
1. What is the primary purpose of an OBD-II system?
A. Increase fuel economy
B. Monitor vehicle emissions and performance
C. Improve tire pressure
D. Control air conditioning
Correct: B
Rationale: OBD-II systems are designed to monitor engine/emission systems for
faults and ensure compliance with emission standards.
2. Which tool is essential for reading diagnostic trouble codes (DTCs)?
A. Multimeter
B. Scan tool
C. Compression tester
D. Timing light
Correct: B
Rationale: A scan tool communicates with the ECU to retrieve stored fault codes.
3. A P0300 code indicates what?
,A. Oxygen sensor failure
B. Random/multiple cylinder misfire
C. Fuel pump failure
D. Battery voltage issue
Correct: B
Rationale: P0300 refers to random or multiple cylinder misfires detected by the
ECU.
4. What does a flashing check engine light usually indicate?
A. Minor fault
B. Severe misfire damaging catalytic converter
C. Low tire pressure
D. Oil change due
Correct: B
Rationale: A flashing MIL indicates a severe misfire that can damage the catalytic
converter.
5. Which sensor measures exhaust oxygen content?
A. MAP sensor
B. Crank sensor
C. O2 sensor
D. TPS
Correct: C
Rationale: The oxygen sensor monitors oxygen levels in exhaust gases for fuel
control.
6. What does a P0171 code indicate?
A. Rich fuel mixture
B. Lean fuel mixture
, C. Ignition failure
D. Transmission fault
Correct: B
Rationale: P0171 indicates system too lean (bank 1).
7. Which component controls ignition timing in modern vehicles?
A. Distributor
B. ECU/PCM
C. Carburetor
D. Alternator
Correct: B
Rationale: The ECU electronically controls ignition timing based on sensor input.
8. What is the function of the MAP sensor?
A. Measures airflow temperature
B. Measures manifold pressure
C. Controls fuel pump
D. Measures battery voltage
Correct: B
Rationale: MAP sensor measures intake manifold pressure to determine engine
load.
9. A dead battery typically reads how many volts?
A. 12.6V
B. 13.8V
C. Below 12.0V
D. 14.5V
Correct: C
Rationale: A fully discharged battery is typically below 12 volts.
question with correct answers
(100% verified answers) plus rationales Q &A
2026 INSTANT DOWNLOAD PDF
1. What is the primary purpose of an OBD-II system?
A. Increase fuel economy
B. Monitor vehicle emissions and performance
C. Improve tire pressure
D. Control air conditioning
Correct: B
Rationale: OBD-II systems are designed to monitor engine/emission systems for
faults and ensure compliance with emission standards.
2. Which tool is essential for reading diagnostic trouble codes (DTCs)?
A. Multimeter
B. Scan tool
C. Compression tester
D. Timing light
Correct: B
Rationale: A scan tool communicates with the ECU to retrieve stored fault codes.
3. A P0300 code indicates what?
,A. Oxygen sensor failure
B. Random/multiple cylinder misfire
C. Fuel pump failure
D. Battery voltage issue
Correct: B
Rationale: P0300 refers to random or multiple cylinder misfires detected by the
ECU.
4. What does a flashing check engine light usually indicate?
A. Minor fault
B. Severe misfire damaging catalytic converter
C. Low tire pressure
D. Oil change due
Correct: B
Rationale: A flashing MIL indicates a severe misfire that can damage the catalytic
converter.
5. Which sensor measures exhaust oxygen content?
A. MAP sensor
B. Crank sensor
C. O2 sensor
D. TPS
Correct: C
Rationale: The oxygen sensor monitors oxygen levels in exhaust gases for fuel
control.
6. What does a P0171 code indicate?
A. Rich fuel mixture
B. Lean fuel mixture
, C. Ignition failure
D. Transmission fault
Correct: B
Rationale: P0171 indicates system too lean (bank 1).
7. Which component controls ignition timing in modern vehicles?
A. Distributor
B. ECU/PCM
C. Carburetor
D. Alternator
Correct: B
Rationale: The ECU electronically controls ignition timing based on sensor input.
8. What is the function of the MAP sensor?
A. Measures airflow temperature
B. Measures manifold pressure
C. Controls fuel pump
D. Measures battery voltage
Correct: B
Rationale: MAP sensor measures intake manifold pressure to determine engine
load.
9. A dead battery typically reads how many volts?
A. 12.6V
B. 13.8V
C. Below 12.0V
D. 14.5V
Correct: C
Rationale: A fully discharged battery is typically below 12 volts.
