VEHICLE COMMUNICATION
SYSTEM LATEST ACTUAL EXAM
2026/2027 | Verified Q&A | Pass
Guaranteed - A+ Graded
Section A: Fundamentals of In-Vehicle Networks (Q1–15)
Q1: On a high-speed CAN bus (ISO 11898-2) in recessive state, the typical voltages on CAN H and CAN L
relative to ground are:
A. CAN H = 5.0V, CAN L = 0V
B. CAN H = 2.5V, CAN L = 2.5V [CORRECT]
C. CAN H = 3.5V, CAN L = 1.5V
D. CAN H = 0V, CAN L = 5.0V
Correct Answer: B
Rationale: In the recessive (logic 1) state, both CAN H and CAN L are biased to approximately 2.5V by
the termination resistors and transceiver, producing a differential voltage near 0V.
Q2: A technician measures 60 ohms between CAN H and CAN L at the DLC under the dashboard. The
vehicle has two terminating resistors. This reading indicates:
A. One missing termination resistor
B. Both termination resistors are present and functioning correctly [CORRECT]
C. A short between CAN H and CAN L
D. An open circuit in both wires
Correct Answer: B
Rationale: Two 120-ohm resistors in parallel equal 60 ohms. Measuring 60 ohms at the DLC confirms
both terminating resistors are present and the bus wiring is continuous.
Q3: The primary advantage of a differential signaling protocol like CAN over single-wire protocols is:
,A. Lower cost of wiring harness
B. Immunity to electromagnetic interference and common-mode noise rejection [CORRECT]
C. Simpler connector design
D. Reduced need for termination resistors
Correct Answer: B
Rationale: Differential signaling transmits data as the voltage difference between two wires. Any
external noise coupled onto both lines equally (common-mode noise) is rejected at the receiver, making
CAN highly robust in the electrically noisy automotive environment.
Q4: In a vehicle with multiple CAN buses (e.g., powertrain CAN, body CAN, infotainment CAN), the
component responsible for routing messages between different networks is called a:
A. Network terminator
B. Gateway module [CORRECT]
C. Bus master controller
D. Protocol converter
Correct Answer: B
Rationale: A gateway module acts as an intelligent router between vehicle networks with different
protocols, speeds, or security domains. It filters, translates, and forwards messages only as configured
by the manufacturer.
Q5: A technician is diagnosing a 2026 model vehicle and notices the scan tool communicates with the
ECM but not the BCM. The most likely explanation is:
A. The scan tool firmware is outdated
B. The ECM and BCM are on separate buses with a faulty gateway [CORRECT]
C. The BCM has no terminating resistor
D. The OBD-II port pin 16 has no power
Correct Answer: B
Rationale: When one module on a network is accessible and another is not, and both are known
functional, the issue typically lies in the interconnection between their respective buses—most
commonly a gateway module that has failed to route or translate messages between subnets.
Q6: The ISO 11898 standard specifies that a high-speed CAN bus must be terminated with:
A. One 60-ohm resistor at the DLC
B. Two 120-ohm resistors, one at each physical end of the bus [CORRECT]
,C. Four 30-ohm resistors distributed along the bus
D. No termination resistors required
Correct Answer: B
Rationale: High-speed CAN (ISO 11898-2) requires two 120-ohm termination resistors placed at the
physical extremes of the bus to prevent signal reflections and ensure proper impedance matching for
signal integrity at 500 kbps or higher.
Q7: A vehicle network uses a single master node that polls multiple slave nodes in a predetermined
sequence. This describes which protocol?
A. High-speed CAN
B. LIN (Local Interconnect Network) [CORRECT]
C. FlexRay
D. Automotive Ethernet
Correct Answer: B
Rationale: LIN uses a single-master, multiple-slave architecture where the master node controls bus
access through a schedule table, polling each slave in a defined sequence. This deterministic approach is
ideal for low-cost, low-speed body electronics like door modules and seat controls.
Q8: The OBD-II diagnostic connector (SAE J1962) specifies that CAN H is located on pin:
A. Pin 6 [CORRECT]
B. Pin 14
C. Pin 7
D. Pin 16
Correct Answer: A
Rationale: SAE J1962 defines pin 6 as CAN High (CAN H) and pin 14 as CAN Low (CAN L) for ISO 15765-4
(CAN) diagnostics. Pin 16 is battery positive, and pin 7 is ISO 9141-2 K-line.
Q9: A network fault code beginning with "U" (e.g., U0100) indicates:
A. Powertrain system fault
B. Network communication fault [CORRECT]
C. Chassis system fault
D. Body system fault
, Correct Answer: B
Rationale: Per SAE J2012/ISO 15031-6, DTCs are categorized by letter prefix: P = Powertrain, C = Chassis,
B = Body, and U = Network/Communication. U-codes specifically indicate bus off conditions, lost
communication, or invalid data between modules.
Q10: In a CAN bus arbitration process, which message ID will always win arbitration and be transmitted
first?
A. The message with the highest numeric ID value
B. The message with the lowest numeric ID value [CORRECT]
C. The message from the module with the highest priority number
D. The message that was queued first in the transmit buffer
Correct Answer: B
Rationale: CAN uses non-destructive bitwise arbitration where dominant (0) bits override recessive (1)
bits. A lower ID value has more dominant bits in the arbitration field, giving it higher priority and
ensuring it wins contention.
Q11: A technician measures 0 ohms between CAN H and ground. The most likely fault condition is:
A. CAN H is shorted to ground [CORRECT]
B. CAN L is shorted to power
C. Both termination resistors are missing
D. The bus is in recessive state
Correct Answer: A
Rationale: A direct measurement of 0 ohms between CAN H and ground indicates a hard short circuit
between the CAN H wire and chassis ground, which will pull the entire bus low and prevent any module
from communicating.
Q12: The maximum recommended total bus length for a high-speed CAN network at 500 kbps is
approximately:
A. 10 meters
B. 40 meters [CORRECT]
C. 100 meters
D. 500 meters
Correct Answer: B
Rationale: ISO 11898-2 specifies that at 500 kbps, the maximum total bus length is approximately 40
SYSTEM LATEST ACTUAL EXAM
2026/2027 | Verified Q&A | Pass
Guaranteed - A+ Graded
Section A: Fundamentals of In-Vehicle Networks (Q1–15)
Q1: On a high-speed CAN bus (ISO 11898-2) in recessive state, the typical voltages on CAN H and CAN L
relative to ground are:
A. CAN H = 5.0V, CAN L = 0V
B. CAN H = 2.5V, CAN L = 2.5V [CORRECT]
C. CAN H = 3.5V, CAN L = 1.5V
D. CAN H = 0V, CAN L = 5.0V
Correct Answer: B
Rationale: In the recessive (logic 1) state, both CAN H and CAN L are biased to approximately 2.5V by
the termination resistors and transceiver, producing a differential voltage near 0V.
Q2: A technician measures 60 ohms between CAN H and CAN L at the DLC under the dashboard. The
vehicle has two terminating resistors. This reading indicates:
A. One missing termination resistor
B. Both termination resistors are present and functioning correctly [CORRECT]
C. A short between CAN H and CAN L
D. An open circuit in both wires
Correct Answer: B
Rationale: Two 120-ohm resistors in parallel equal 60 ohms. Measuring 60 ohms at the DLC confirms
both terminating resistors are present and the bus wiring is continuous.
Q3: The primary advantage of a differential signaling protocol like CAN over single-wire protocols is:
,A. Lower cost of wiring harness
B. Immunity to electromagnetic interference and common-mode noise rejection [CORRECT]
C. Simpler connector design
D. Reduced need for termination resistors
Correct Answer: B
Rationale: Differential signaling transmits data as the voltage difference between two wires. Any
external noise coupled onto both lines equally (common-mode noise) is rejected at the receiver, making
CAN highly robust in the electrically noisy automotive environment.
Q4: In a vehicle with multiple CAN buses (e.g., powertrain CAN, body CAN, infotainment CAN), the
component responsible for routing messages between different networks is called a:
A. Network terminator
B. Gateway module [CORRECT]
C. Bus master controller
D. Protocol converter
Correct Answer: B
Rationale: A gateway module acts as an intelligent router between vehicle networks with different
protocols, speeds, or security domains. It filters, translates, and forwards messages only as configured
by the manufacturer.
Q5: A technician is diagnosing a 2026 model vehicle and notices the scan tool communicates with the
ECM but not the BCM. The most likely explanation is:
A. The scan tool firmware is outdated
B. The ECM and BCM are on separate buses with a faulty gateway [CORRECT]
C. The BCM has no terminating resistor
D. The OBD-II port pin 16 has no power
Correct Answer: B
Rationale: When one module on a network is accessible and another is not, and both are known
functional, the issue typically lies in the interconnection between their respective buses—most
commonly a gateway module that has failed to route or translate messages between subnets.
Q6: The ISO 11898 standard specifies that a high-speed CAN bus must be terminated with:
A. One 60-ohm resistor at the DLC
B. Two 120-ohm resistors, one at each physical end of the bus [CORRECT]
,C. Four 30-ohm resistors distributed along the bus
D. No termination resistors required
Correct Answer: B
Rationale: High-speed CAN (ISO 11898-2) requires two 120-ohm termination resistors placed at the
physical extremes of the bus to prevent signal reflections and ensure proper impedance matching for
signal integrity at 500 kbps or higher.
Q7: A vehicle network uses a single master node that polls multiple slave nodes in a predetermined
sequence. This describes which protocol?
A. High-speed CAN
B. LIN (Local Interconnect Network) [CORRECT]
C. FlexRay
D. Automotive Ethernet
Correct Answer: B
Rationale: LIN uses a single-master, multiple-slave architecture where the master node controls bus
access through a schedule table, polling each slave in a defined sequence. This deterministic approach is
ideal for low-cost, low-speed body electronics like door modules and seat controls.
Q8: The OBD-II diagnostic connector (SAE J1962) specifies that CAN H is located on pin:
A. Pin 6 [CORRECT]
B. Pin 14
C. Pin 7
D. Pin 16
Correct Answer: A
Rationale: SAE J1962 defines pin 6 as CAN High (CAN H) and pin 14 as CAN Low (CAN L) for ISO 15765-4
(CAN) diagnostics. Pin 16 is battery positive, and pin 7 is ISO 9141-2 K-line.
Q9: A network fault code beginning with "U" (e.g., U0100) indicates:
A. Powertrain system fault
B. Network communication fault [CORRECT]
C. Chassis system fault
D. Body system fault
, Correct Answer: B
Rationale: Per SAE J2012/ISO 15031-6, DTCs are categorized by letter prefix: P = Powertrain, C = Chassis,
B = Body, and U = Network/Communication. U-codes specifically indicate bus off conditions, lost
communication, or invalid data between modules.
Q10: In a CAN bus arbitration process, which message ID will always win arbitration and be transmitted
first?
A. The message with the highest numeric ID value
B. The message with the lowest numeric ID value [CORRECT]
C. The message from the module with the highest priority number
D. The message that was queued first in the transmit buffer
Correct Answer: B
Rationale: CAN uses non-destructive bitwise arbitration where dominant (0) bits override recessive (1)
bits. A lower ID value has more dominant bits in the arbitration field, giving it higher priority and
ensuring it wins contention.
Q11: A technician measures 0 ohms between CAN H and ground. The most likely fault condition is:
A. CAN H is shorted to ground [CORRECT]
B. CAN L is shorted to power
C. Both termination resistors are missing
D. The bus is in recessive state
Correct Answer: A
Rationale: A direct measurement of 0 ohms between CAN H and ground indicates a hard short circuit
between the CAN H wire and chassis ground, which will pull the entire bus low and prevent any module
from communicating.
Q12: The maximum recommended total bus length for a high-speed CAN network at 500 kbps is
approximately:
A. 10 meters
B. 40 meters [CORRECT]
C. 100 meters
D. 500 meters
Correct Answer: B
Rationale: ISO 11898-2 specifies that at 500 kbps, the maximum total bus length is approximately 40
