OBD II Systems – Certification Examination
OBD II SYSTEMS – ON-BOARD DIAGNOSTICS II EXAM QUESTIONS AND
CORRECT ANSWERS | LATEST 2026/2027
ON-BOARD DIAGNOSTICS II (OBD II) SYSTEMS
1. The OBD II requirement became mandatory for all new light-duty
passenger cars and trucks sold in the United States beginning with
which model year?
A. 1996
B. 2001
C. 1994
D. 1988
A. 1996
Federal and CARB rules required full OBD II compliance on all light-duty
vehicles sold in the U.S. starting with the 1996 model year.
2. Which agency first developed the OBD regulations that later became
the basis for the federal OBD II program?
A. Department of Energy (DOE)
B. Society of Automotive Engineers (SAE)
C. California Air Resources Board (CARB)
D. National Highway Traffic Safety Administration (NHTSA)
C. California Air Resources Board (CARB)
CARB introduced OBD I in 1988 and OBD II requirements in California
before the EPA adopted them nationally.
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, OBD II Systems – Certification Examination
3. The primary purpose of an OBD II system is to:
A. Record crash data for insurance purposes
B. Monitor emission-related components and alert the driver when
emissions may exceed allowable limits
C. Control vehicle speed during cruise operation
D. Prevent theft by disabling the ignition
B. Monitor emission-related components and alert the driver when
emissions may exceed allowable limits
OBD II exists to detect faults that could raise tailpipe or evaporative
emissions beyond about 1.5 times the certified standard.
4. The OBD II Data Link Connector (DLC) is defined by which SAE
standard?
A. SAE J1939
B. SAE J1962
C. SAE J1979
D. SAE J2534
B. SAE J1962
J1962 specifies the 16-pin connector shape, pin assignments and its
location in the passenger compartment.
5. How many pins does the standard OBD II DLC contain?
A. 12
B. 9
C. 20
D. 16
D. 16
The J1962 connector is a 16-cavity, D-shaped connector arranged in two
rows of eight.
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, OBD II Systems – Certification Examination
6. Where must the OBD II DLC be located on a compliant vehicle?
A. Behind the rear bumper
B. In the engine compartment near the PCM
C. Within the passenger compartment, generally under the dash near the
steering column
D. In the trunk near the battery
C. Within the passenger compartment, generally under the dash near
the steering column
Regulations require the DLC to be accessible from the driver's seat area,
typically within about 12 inches of the vehicle centerline.
7. On the J1962 connector, pin 16 provides:
A. CAN High
B. Chassis ground
C. K-Line
D. Unswitched battery positive (B+)
D. Unswitched battery positive (B+)
Pin 16 supplies constant battery voltage so the scan tool can power up
from the vehicle.
8. Which DLC pins are used for ISO 15765 CAN communication?
A. Pins 4 and 5
B. Pins 6 and 14
C. Pins 7 and 15
D. Pins 2 and 10
B. Pins 6 and 14
Pin 6 is CAN High and pin 14 is CAN Low on the standard OBD II
connector.
9. Pins 4 and 5 of the OBD II connector are assigned to:
A. K-Line and L-Line
B. Chassis ground and signal ground
C. Battery positive and ignition
D. CAN High and CAN Low
B. Chassis ground and signal ground
Pin 4 is chassis ground and pin 5 is signal ground for the scan tool.
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, OBD II Systems – Certification Examination
10. Pin 7 on the DLC is used for which communication line?
A. ISO 9141-2 / ISO 14230 K-Line
B. CAN Low
C. SAE J1850 PWM bus minus
D. SAE J1850 VPW bus
A. ISO 9141-2 / ISO 14230 K-Line
The K-Line on pin 7 carries ISO 9141-2 and KWP2000 data; pin 15 is the
optional L-Line.
11. SAE J1850 VPW communication is carried on which DLC pin?
A. Pin 14
B. Pin 6
C. Pin 2
D. Pin 7
C. Pin 2
VPW uses a single wire on pin 2; PWM uses pins 2 and 10 as a differential
pair.
12. SAE J1850 PWM communication was historically associated with
which manufacturer?
A. Toyota
B. Chrysler
C. Ford
D. General Motors
C. Ford
Ford used the 41.6 kbps PWM protocol, while GM primarily used 10.4
kbps VPW.
13. Beginning with which model year did the U.S. require CAN (ISO
15765-4) as the OBD II communication protocol on all new light-duty
vehicles?
A. 2003
B. 1996
C. 2012
D. 2008
D. 2008
CAN became mandatory for OBD II diagnostics on all U.S. light-duty
vehicles from the 2008 model year.
Page 4 of 54
OBD II SYSTEMS – ON-BOARD DIAGNOSTICS II EXAM QUESTIONS AND
CORRECT ANSWERS | LATEST 2026/2027
ON-BOARD DIAGNOSTICS II (OBD II) SYSTEMS
1. The OBD II requirement became mandatory for all new light-duty
passenger cars and trucks sold in the United States beginning with
which model year?
A. 1996
B. 2001
C. 1994
D. 1988
A. 1996
Federal and CARB rules required full OBD II compliance on all light-duty
vehicles sold in the U.S. starting with the 1996 model year.
2. Which agency first developed the OBD regulations that later became
the basis for the federal OBD II program?
A. Department of Energy (DOE)
B. Society of Automotive Engineers (SAE)
C. California Air Resources Board (CARB)
D. National Highway Traffic Safety Administration (NHTSA)
C. California Air Resources Board (CARB)
CARB introduced OBD I in 1988 and OBD II requirements in California
before the EPA adopted them nationally.
Page 1 of 54
, OBD II Systems – Certification Examination
3. The primary purpose of an OBD II system is to:
A. Record crash data for insurance purposes
B. Monitor emission-related components and alert the driver when
emissions may exceed allowable limits
C. Control vehicle speed during cruise operation
D. Prevent theft by disabling the ignition
B. Monitor emission-related components and alert the driver when
emissions may exceed allowable limits
OBD II exists to detect faults that could raise tailpipe or evaporative
emissions beyond about 1.5 times the certified standard.
4. The OBD II Data Link Connector (DLC) is defined by which SAE
standard?
A. SAE J1939
B. SAE J1962
C. SAE J1979
D. SAE J2534
B. SAE J1962
J1962 specifies the 16-pin connector shape, pin assignments and its
location in the passenger compartment.
5. How many pins does the standard OBD II DLC contain?
A. 12
B. 9
C. 20
D. 16
D. 16
The J1962 connector is a 16-cavity, D-shaped connector arranged in two
rows of eight.
Page 2 of 54
, OBD II Systems – Certification Examination
6. Where must the OBD II DLC be located on a compliant vehicle?
A. Behind the rear bumper
B. In the engine compartment near the PCM
C. Within the passenger compartment, generally under the dash near the
steering column
D. In the trunk near the battery
C. Within the passenger compartment, generally under the dash near
the steering column
Regulations require the DLC to be accessible from the driver's seat area,
typically within about 12 inches of the vehicle centerline.
7. On the J1962 connector, pin 16 provides:
A. CAN High
B. Chassis ground
C. K-Line
D. Unswitched battery positive (B+)
D. Unswitched battery positive (B+)
Pin 16 supplies constant battery voltage so the scan tool can power up
from the vehicle.
8. Which DLC pins are used for ISO 15765 CAN communication?
A. Pins 4 and 5
B. Pins 6 and 14
C. Pins 7 and 15
D. Pins 2 and 10
B. Pins 6 and 14
Pin 6 is CAN High and pin 14 is CAN Low on the standard OBD II
connector.
9. Pins 4 and 5 of the OBD II connector are assigned to:
A. K-Line and L-Line
B. Chassis ground and signal ground
C. Battery positive and ignition
D. CAN High and CAN Low
B. Chassis ground and signal ground
Pin 4 is chassis ground and pin 5 is signal ground for the scan tool.
Page 3 of 54
, OBD II Systems – Certification Examination
10. Pin 7 on the DLC is used for which communication line?
A. ISO 9141-2 / ISO 14230 K-Line
B. CAN Low
C. SAE J1850 PWM bus minus
D. SAE J1850 VPW bus
A. ISO 9141-2 / ISO 14230 K-Line
The K-Line on pin 7 carries ISO 9141-2 and KWP2000 data; pin 15 is the
optional L-Line.
11. SAE J1850 VPW communication is carried on which DLC pin?
A. Pin 14
B. Pin 6
C. Pin 2
D. Pin 7
C. Pin 2
VPW uses a single wire on pin 2; PWM uses pins 2 and 10 as a differential
pair.
12. SAE J1850 PWM communication was historically associated with
which manufacturer?
A. Toyota
B. Chrysler
C. Ford
D. General Motors
C. Ford
Ford used the 41.6 kbps PWM protocol, while GM primarily used 10.4
kbps VPW.
13. Beginning with which model year did the U.S. require CAN (ISO
15765-4) as the OBD II communication protocol on all new light-duty
vehicles?
A. 2003
B. 1996
C. 2012
D. 2008
D. 2008
CAN became mandatory for OBD II diagnostics on all U.S. light-duty
vehicles from the 2008 model year.
Page 4 of 54
