Feb 15 • Case studies
Case Study: CAN Faults!! GMC Sierra 1500 1500
Vehicle Information
Make/Model:GMC Sierra
Year: 2014
Mileage:126,467
Customer Concern
The customer reported that the instrumentation cluster on their GMC Sierra was behaving erratically, especially while driving over bumpy roads. This issue was highly duplicatable and presented a significant safety concern.
Initial Inspection
During the initial visual inspection, the following observations were made:
The instrumentation cluster exhibited erratic behavior when driving over uneven surfaces.
The issue was easily replicable by rocking the vehicle in the parking lot, indicating a potential physical fault.
The Diagnostic Process
Initial Diagnosis and DTC Retrieval
Connected the scan tool to retrieve Diagnostic Trouble Codes (DTCs).
Detected CAN communication faults across every module in the vehicle, indicating a systemic issue affecting the entire network.
Physical Inspection
Conducted a thorough visual inspection of the vehicle's undercarriage and suspension components.
Identified a broken shock mount at the rear of the vehicle, suggesting that significant stress and movement had been affecting nearby components.
Chafed Harness Detection
Focused on the area around the broken shock mount for potential wiring issues.
Discovered a chafe in the harness near the broken mount location. The constant movement and vibration caused by the broken mount had led to the insulation wearing down, exposing the wires and causing intermittent CAN communication faults.
Harness Repair and Temporary Solution
Isolated the chafed section of the harness and repaired the damaged wires to restore proper insulation and connectivity.
Rerouted the harness away from the broken mount to prevent further damage.
This fix was implemented as a temporary solution to allow the customer to continue using the vehicle while arranging for the frame and shock mount to be permanently repaired.
Technical Analysis
CAN Network Impact: The chafed harness near the broken shock mount caused intermittent short circuits and open circuits, which disrupted the CAN communication network across all modules. This resulted in erratic behavior of the instrumentation cluster and other electronic systems.
Vibration and Movement: The damaged shock mount allowed excessive movement and vibration, exacerbating the chafing of the harness and worsening the CAN communication faults.
Temporary vs. Permanent Repair: While the temporary harness repair and rerouting restored functionality, it was essential for the customer to address the underlying mechanical issue (broken shock mount and frame) to prevent future occurrences.
Conclusion
This case study highlights the importance of a thorough diagnostic process that includes both electronic and physical inspections. The discovery of the chafed harness and broken shock mount underscores the interconnected nature of mechanical and electronic systems in modern vehicles. By addressing the immediate issue with a temporary fix and advising the customer on the necessary permanent repairs, we ensured the vehicle's continued safe operation while allowing time for comprehensive maintenance.
This comprehensive approach to diagnosing and resolving the CAN communication faults in the GMC Sierra not only solved the immediate problem but also provided valuable insights into preventing future issues.
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Case Study: CAN Faults!! GMC Sierra 1500 1500
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