Excavator: No Communication with Machine Controller on Cold Mornings

Confirmed cause: A factory splice in the CAN bus harness located under the cab floor mat was found to have a cold solder joint. The splice connected the main bus to the diagnostic port. On cold mornings, the joint would contract and create high resistance, disrupting the entire network. As the cab warmed up, the joint would expand, continuity would be restored, and the network would function correctly. Repair performed: The faulty factory splice was removed. The wires were re-spliced using an environmentally sealed, crimp-and-solder butt connector and protected with heat shrink tubing to ensure a durable and weather-resistant connection. Verification: The machine was left overnight in freezing temperatures. The following morning, the machine was started and no communication errors were present on the monitor. All functions were immediately available. CAN bus resistance was checked cold and measured a stable reading that met the manufacturer's specification. Technician notes: - This fault was difficult to isolate because it only occurred when cold. - Using a portable heater to warm specific areas and components was critical to narrowing down the problem location. - Do not assume a fluctuating resistance reading is a bad meter; it is often a sign of a poor connection. - CAN bus issues that are temperature-sensitive often lead back to bad solder joints, pin connections, or hairline cracks in circuit boards or harnesses.