VEHICLE COMMUNICATION SYSTEM (LATEST) QUESTIONS AND ANSWERS 100% CORRECT 2026/2027 2026/2027 | Page 1 | Passing Score: 80%
VEHICLE COMMUNICATION SYSTEMS
VEHICLE COMMUNICATION SYSTEM (LATEST)
QUESTIONS AND ANSWERS 100% CORRECT 2026/2027
VEHICLE COMMUNICATIONS | Official Exam 2026/2027
75 80% CERTIFIED
QUESTIONS PASSING SCORE RECERTIFICATION
TABLE OF CONTENTS
Section 1 CAN Protocol & Network Architecture Q1-18
Section 2 LIN, FlexRay & Additional Bus Protocols Q19-33
Section 3 Automotive Ethernet & IP-Based Communication Q34-48
Section 4 Diagnostics & Troubleshooting Protocols Q49-63
Section 5 V2X Communication & Emerging Technologies Q64-75
Instructions: Select the single best answer for each question. This exam is designed for Vehicle Communication System certification
preparation. Passing score: 80% (60 questions correct).
VEHICLE COMMUNICATION SYSTEM (LATEST) QUESTIONS AND ANSWERS 100% CORRECT 2026/2027 -- 2026/2027 | Passing Score: 80% | Page 1
,(LATEST) Q&A 100% CORRECT 2026/2027 2026/2027
SECTION 1 | CAN PROTOCOL & NETWORK ARCHITECTURE | Q1-Q18 | VEHICLE COMMUNICATION SYSTEM
Q1 Question 1 of 75
A powertrain ECU in a 2021 sedan broadcasts engine-rpm messages using an 11-bit identifier
field on the high-speed CAN bus. The body-control module on the same bus was designed for an
earlier platform and expects only standard-format frames. During integration testing the engineer
observes that the body-control module silently discards these messages. The message structure
uses a 29-bit identifier by mistake in the arbitration phase. The root cause is most directly related
to the difference between
A. CAN 2.0A standard frames that use 11-bit identifiers and CAN 2.0B extended frames that
use 29-bit identifiers
B. the data-field length being 8 bytes in CAN 2.0A versus 64 bytes in CAN 2.0B
C. the CRC polynomial differing between CAN 2.0A and CAN 2.0B frame formats
D. the inter-frame spacing being fixed in CAN 2.0A but variable in CAN 2.0B
Correct Answer: A
Rationale:
CAN 2.0A defines the standard frame format with an 11-bit identifier, while CAN 2.0B introduces the
extended format with a 29-bit identifier. A node that only supports CAN 2.0A will discard any
extended-format frame because it cannot parse the longer arbitration field. Option B is wrong because both
CAN 2.0A and 2.0B classic frames are limited to 8 data bytes; the 64-byte payload is a CAN FD feature.
Q2 Question 2 of 75
A validation engineer is reviewing a captured CAN bus trace at the bit level on a heavy-duty
truck's J1939 network. The trace shows a single dominant bit immediately before the arbitration
field on every successfully transmitted frame. The engineer needs to confirm the purpose of this
dominant bit in the overall frame structure. This bit serves the function of
A. signaling the start of the CRC check sequence to all receivers on the bus
B. marking the beginning of the frame and synchronizing all nodes to the same starting
point
C. indicating whether the following frame uses a standard or extended identifier format
D. requesting a retransmission of the previously lost frame from the sending node
Correct Answer: B
Rationale:
The Start-Of-Frame (SOF) bit is a single dominant bit that signals the start of every CAN frame and allows
all nodes to synchronize to the incoming message. It is not related to CRC, identifier type, or
retransmission. Option A incorrectly associates the dominant bit with the CRC sequence, which appears
much later in the frame.
VEHICLE COMMUNICATION SYSTEM (LATEST) QUESTIONS AND ANSWERS 100% CORRECT 2026/2027 -- 2026/2027 | Passing Score: 80% | Page 2
,Q3 Question 3 of 75
Two ECUs in a hybrid vehicle attempt simultaneous transmission on the same CAN bus: the
inverter ECU sends a frame with ID 0x100 and the battery-management ECU sends a frame with
ID 0x050. Both messages are standard-format data frames. The bus logic resolves the conflict,
and the battery-management ECU wins arbitration without data loss. This outcome occurs
because
A. the battery-management ECU has a higher clock rate and therefore drives the bus level faster
than the inverter ECU
B. the CAN controller in the battery ECU is configured as the master node and always takes priority
on the bus
C. lower numeric identifiers dominate during bitwise arbitration, so 0x050 overwrites 0x100
bit-by-bit
D. the inverter ECU detects a bit error and voluntarily aborts transmission before the arbitration
phase ends
Correct Answer: C
Rationale:
CAN uses non-destructive bitwise arbitration where the node transmitting the recessive bit loses to the
dominant bit. A lower numeric identifier contains more leading dominant bits, so 0x050 wins over 0x100.
Option A is wrong because clock rate does not determine priority in arbitration. Option B is wrong because
CAN has no master-slave relationship.
Q4 Question 4 of 75
During end-of-line testing of an electric-vehicle powertrain CAN bus, an engineer injects a
single-bit error into the data field of a transmitted frame. The receiving ECU immediately flags a
CRC error and sends an error frame. The CRC check in CAN is designed to detect this type of
error because
A. the 15-bit CRC polynomial used in CAN guarantees detection of any single-bit error in the
frame
B. the CRC field is computed over only the arbitration field, so any data-field error causes a
mismatch
C. the CRC algorithm in CAN recalculates checksums for every 8-bit byte boundary in the data field
D. the CRC check uses a 32-bit polynomial that can detect all multi-bit errors up to the frame length
Correct Answer: A
Rationale:
The CAN CRC uses a 15-bit polynomial (x^15 + x^14 + x^10 + x^8 + x^7 + x^4 + x^3 + 1) that
mathematically guarantees detection of any single-bit error across the entire frame. Option B is wrong
because the CRC is computed over the SOF, arbitration, control, and data fields-not just the arbitration field.
Option D is wrong because CAN uses a 15-bit, not 32-bit, CRC.
VEHICLE COMMUNICATION SYSTEM (LATEST) QUESTIONS AND ANSWERS 100% CORRECT 2026/2027 -- 2026/2027 | Passing Score: 80% | Page 3
, Q5 Question 5 of 75
A faulty door-module ECU on a passenger car's body CAN bus repeatedly transmits corrupted
frames, causing its transmit error counter to increment rapidly. After accumulating 256 error
counts, the ECU stops all bus activity entirely and does not resume even after power-cycling the
module. The ECU has entered the state known as
A. error-active, where it continues transmitting but only with passive error flags
B. error-passive, where it transmits passive error flags and must wait eight bit times after each
frame
C. listen-only mode, where it monitors the bus but cannot acknowledge any received frames
D. bus-off, where the controller is disconnected from the bus and requires manual reset or
reintegration logic
Correct Answer: D
Rationale:
When a CAN node's transmit error counter reaches 256, it enters the bus-off state and is effectively
disconnected from bus traffic. Recovery requires specific conditions such as 128 × 11 recessive bits
observed on the bus or an explicit controller reset. Option B describes error-passive (TEC between 128 and
255), not bus-off.
Q6 Question 6 of 75
A chassis-development team is migrating a vehicle's powertrain CAN bus from classic CAN to
CAN FD to accommodate larger sensor datasets from a new ADAS module. During the upgrade,
the team discovers that existing classic CAN nodes sometimes interpret CAN FD frames as
errors. The key feature of CAN FD that causes this incompatibility is that
A. CAN FD uses a different physical layer voltage level that classic CAN transceivers cannot detect
B. CAN FD frames always use a 29-bit identifier, making them unreadable by classic CAN
controllers
C. CAN FD switches to a faster bit rate after the arbitration phase and supports data fields up
to 64 bytes
D. CAN FD eliminates the CRC field to achieve higher throughput, which classic CAN interprets as
a form error
Correct Answer: C
Rationale:
CAN FD (Flexible Data-rate) introduces the BRS (Bit Rate Switch) bit and can increase the bit rate after the
arbitration phase, plus it supports payloads up to 64 bytes. Classic CAN controllers cannot parse these
longer or faster frames. Option A is wrong because CAN FD uses the same physical layer; Option D is
wrong because CAN FD actually has a more robust CRC, not a missing one.
VEHICLE COMMUNICATION SYSTEM (LATEST) QUESTIONS AND ANSWERS 100% CORRECT 2026/2027 -- 2026/2027 | Passing Score: 80% | Page 4
VEHICLE COMMUNICATION SYSTEMS
VEHICLE COMMUNICATION SYSTEM (LATEST)
QUESTIONS AND ANSWERS 100% CORRECT 2026/2027
VEHICLE COMMUNICATIONS | Official Exam 2026/2027
75 80% CERTIFIED
QUESTIONS PASSING SCORE RECERTIFICATION
TABLE OF CONTENTS
Section 1 CAN Protocol & Network Architecture Q1-18
Section 2 LIN, FlexRay & Additional Bus Protocols Q19-33
Section 3 Automotive Ethernet & IP-Based Communication Q34-48
Section 4 Diagnostics & Troubleshooting Protocols Q49-63
Section 5 V2X Communication & Emerging Technologies Q64-75
Instructions: Select the single best answer for each question. This exam is designed for Vehicle Communication System certification
preparation. Passing score: 80% (60 questions correct).
VEHICLE COMMUNICATION SYSTEM (LATEST) QUESTIONS AND ANSWERS 100% CORRECT 2026/2027 -- 2026/2027 | Passing Score: 80% | Page 1
,(LATEST) Q&A 100% CORRECT 2026/2027 2026/2027
SECTION 1 | CAN PROTOCOL & NETWORK ARCHITECTURE | Q1-Q18 | VEHICLE COMMUNICATION SYSTEM
Q1 Question 1 of 75
A powertrain ECU in a 2021 sedan broadcasts engine-rpm messages using an 11-bit identifier
field on the high-speed CAN bus. The body-control module on the same bus was designed for an
earlier platform and expects only standard-format frames. During integration testing the engineer
observes that the body-control module silently discards these messages. The message structure
uses a 29-bit identifier by mistake in the arbitration phase. The root cause is most directly related
to the difference between
A. CAN 2.0A standard frames that use 11-bit identifiers and CAN 2.0B extended frames that
use 29-bit identifiers
B. the data-field length being 8 bytes in CAN 2.0A versus 64 bytes in CAN 2.0B
C. the CRC polynomial differing between CAN 2.0A and CAN 2.0B frame formats
D. the inter-frame spacing being fixed in CAN 2.0A but variable in CAN 2.0B
Correct Answer: A
Rationale:
CAN 2.0A defines the standard frame format with an 11-bit identifier, while CAN 2.0B introduces the
extended format with a 29-bit identifier. A node that only supports CAN 2.0A will discard any
extended-format frame because it cannot parse the longer arbitration field. Option B is wrong because both
CAN 2.0A and 2.0B classic frames are limited to 8 data bytes; the 64-byte payload is a CAN FD feature.
Q2 Question 2 of 75
A validation engineer is reviewing a captured CAN bus trace at the bit level on a heavy-duty
truck's J1939 network. The trace shows a single dominant bit immediately before the arbitration
field on every successfully transmitted frame. The engineer needs to confirm the purpose of this
dominant bit in the overall frame structure. This bit serves the function of
A. signaling the start of the CRC check sequence to all receivers on the bus
B. marking the beginning of the frame and synchronizing all nodes to the same starting
point
C. indicating whether the following frame uses a standard or extended identifier format
D. requesting a retransmission of the previously lost frame from the sending node
Correct Answer: B
Rationale:
The Start-Of-Frame (SOF) bit is a single dominant bit that signals the start of every CAN frame and allows
all nodes to synchronize to the incoming message. It is not related to CRC, identifier type, or
retransmission. Option A incorrectly associates the dominant bit with the CRC sequence, which appears
much later in the frame.
VEHICLE COMMUNICATION SYSTEM (LATEST) QUESTIONS AND ANSWERS 100% CORRECT 2026/2027 -- 2026/2027 | Passing Score: 80% | Page 2
,Q3 Question 3 of 75
Two ECUs in a hybrid vehicle attempt simultaneous transmission on the same CAN bus: the
inverter ECU sends a frame with ID 0x100 and the battery-management ECU sends a frame with
ID 0x050. Both messages are standard-format data frames. The bus logic resolves the conflict,
and the battery-management ECU wins arbitration without data loss. This outcome occurs
because
A. the battery-management ECU has a higher clock rate and therefore drives the bus level faster
than the inverter ECU
B. the CAN controller in the battery ECU is configured as the master node and always takes priority
on the bus
C. lower numeric identifiers dominate during bitwise arbitration, so 0x050 overwrites 0x100
bit-by-bit
D. the inverter ECU detects a bit error and voluntarily aborts transmission before the arbitration
phase ends
Correct Answer: C
Rationale:
CAN uses non-destructive bitwise arbitration where the node transmitting the recessive bit loses to the
dominant bit. A lower numeric identifier contains more leading dominant bits, so 0x050 wins over 0x100.
Option A is wrong because clock rate does not determine priority in arbitration. Option B is wrong because
CAN has no master-slave relationship.
Q4 Question 4 of 75
During end-of-line testing of an electric-vehicle powertrain CAN bus, an engineer injects a
single-bit error into the data field of a transmitted frame. The receiving ECU immediately flags a
CRC error and sends an error frame. The CRC check in CAN is designed to detect this type of
error because
A. the 15-bit CRC polynomial used in CAN guarantees detection of any single-bit error in the
frame
B. the CRC field is computed over only the arbitration field, so any data-field error causes a
mismatch
C. the CRC algorithm in CAN recalculates checksums for every 8-bit byte boundary in the data field
D. the CRC check uses a 32-bit polynomial that can detect all multi-bit errors up to the frame length
Correct Answer: A
Rationale:
The CAN CRC uses a 15-bit polynomial (x^15 + x^14 + x^10 + x^8 + x^7 + x^4 + x^3 + 1) that
mathematically guarantees detection of any single-bit error across the entire frame. Option B is wrong
because the CRC is computed over the SOF, arbitration, control, and data fields-not just the arbitration field.
Option D is wrong because CAN uses a 15-bit, not 32-bit, CRC.
VEHICLE COMMUNICATION SYSTEM (LATEST) QUESTIONS AND ANSWERS 100% CORRECT 2026/2027 -- 2026/2027 | Passing Score: 80% | Page 3
, Q5 Question 5 of 75
A faulty door-module ECU on a passenger car's body CAN bus repeatedly transmits corrupted
frames, causing its transmit error counter to increment rapidly. After accumulating 256 error
counts, the ECU stops all bus activity entirely and does not resume even after power-cycling the
module. The ECU has entered the state known as
A. error-active, where it continues transmitting but only with passive error flags
B. error-passive, where it transmits passive error flags and must wait eight bit times after each
frame
C. listen-only mode, where it monitors the bus but cannot acknowledge any received frames
D. bus-off, where the controller is disconnected from the bus and requires manual reset or
reintegration logic
Correct Answer: D
Rationale:
When a CAN node's transmit error counter reaches 256, it enters the bus-off state and is effectively
disconnected from bus traffic. Recovery requires specific conditions such as 128 × 11 recessive bits
observed on the bus or an explicit controller reset. Option B describes error-passive (TEC between 128 and
255), not bus-off.
Q6 Question 6 of 75
A chassis-development team is migrating a vehicle's powertrain CAN bus from classic CAN to
CAN FD to accommodate larger sensor datasets from a new ADAS module. During the upgrade,
the team discovers that existing classic CAN nodes sometimes interpret CAN FD frames as
errors. The key feature of CAN FD that causes this incompatibility is that
A. CAN FD uses a different physical layer voltage level that classic CAN transceivers cannot detect
B. CAN FD frames always use a 29-bit identifier, making them unreadable by classic CAN
controllers
C. CAN FD switches to a faster bit rate after the arbitration phase and supports data fields up
to 64 bytes
D. CAN FD eliminates the CRC field to achieve higher throughput, which classic CAN interprets as
a form error
Correct Answer: C
Rationale:
CAN FD (Flexible Data-rate) introduces the BRS (Bit Rate Switch) bit and can increase the bit rate after the
arbitration phase, plus it supports payloads up to 64 bytes. Classic CAN controllers cannot parse these
longer or faster frames. Option A is wrong because CAN FD uses the same physical layer; Option D is
wrong because CAN FD actually has a more robust CRC, not a missing one.
VEHICLE COMMUNICATION SYSTEM (LATEST) QUESTIONS AND ANSWERS 100% CORRECT 2026/2027 -- 2026/2027 | Passing Score: 80% | Page 4
