The diagnostics for the ECM are accessed through one of the following: the Operator Monitoring System or the Cat® Electronic Technician (ET) Service Tool. When troubleshooting the electronic control system of the machine, additional information is required from the Service Manual for the machine. The following list of the recommended support materials:
- Electrical Schematic, UENR6662, "303.5E2 CR Mini Hydraulic Excavator Electrical System (Interactive)".
- Hydraulic Schematic, UENR5188, "303.5E2 CR, 304E2 CR, 304.5E2 XTC, 305E2 CR, 305.5E2 CR Mini Excavator Hydraulic System (Interactive)".
- Operation and Maintenance, SEBU9418, "303.5E2 CR and 305.5E2 CR Mini Hydraulic Excavators".
- System Operation, UENR4294, "303.5E2 CR, 304E2 CR, 305E2 CR, and 305.5E2 CR Mini Hydraulic".
- Systems Operation, UENR4711, "303.5E2, 304.5E2 XTC, 305.5E2, 305E2, 307E2, 308E2 CR, and 308E2 SR Mini Hydraulic Excavators E2-Series Mini Hex Monitor."
As a guide, an abbreviated version of the system schematic is included at the end of this manual. For an accurate representation of the electrical system , refer to Electrical System Schematic, UENR6662.
When the troubleshooting procedure instructs you to “REPAIR THE HARNESS OR REPLACE THE HARNESS”, use the Electrical System Schematic to trace the circuit. Perform continuity checks at the harness connectors to locate harness failures. At the connectors of the components, always check the ground circuit. Less than 5 Ω of resistance is required between the ground contacts of the connector and the frame ground. The power circuits of the ECM should have less than 2 Ω of resistance between the contacts of the ground connector and the frame ground. Less than 5 Ω of resistance is required for signal circuits for normal operation. Excessive ground resistance that is greater than 5 Ω can cause incorrect diagnosing of problems.
During troubleshooting, inspect all connections before replacing any components. If these connections are not clean and tight, permanent electrical problems or intermittent electrical problems can result. Check that the wires are pushed into the connectors completely. Make sure that the connections are tight before other tests are made.
Failure of an electrical component can cause the failure of other components. Also, failure of an electrical component can be caused by the failure of other components. Always attempt to correct the cause of an electrical system failure before you replace a component.
Note: Some machines may not include all troubleshooting capabilities listed in this manual.