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Heavy Duty Equipment Technician Red Seal Exam Prep · Question

A technician is troubleshooting a fault code indicating a 'CAN Communication Error' on an articulated dump truck. Live data shows that several ECUs are not responding. What is the most crucial step to perform first when diagnosing a widespread CAN communication issue?

Before checking power/ground to individual ECUs or considering replacing components or software updates, a physical inspection of the CAN-bus wiring, including

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Question: A technician is troubleshooting a fault code indicating a 'CAN Communication Error' on an articulated dump truck. Live data shows that several ECUs are not responding. What is the most crucial step to perform first when diagnosing a widespread CAN communication issue?

Answer options:

  • Check power and ground supply to all non-communicating ECUs.
  • Replace the main vehicle control unit (VCU).
  • Perform a software update on all ECUs. ✅ Inspect the CAN-bus wires for physical damage or unplugged connectors.

Correct answer: Inspect the CAN-bus wires for physical damage or unplugged connectors.

Explanation: Before checking power/ground to individual ECUs or considering replacing components or software updates, a physical inspection of the CAN-bus wiring, including connectors and termination resistors, is the most crucial first step for a 'widespread' communication error. Physical damage or loose connections often directly lead to bus communication failures. Power/ground checks would follow if the bus structure appears intact.

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