DOWEL 7T5886 - Caterpillar

Troubleshooting the electronic control modules of the tractor requires additional information from the machine Service Manual, the Electrical System Schematic, and the Operation and Maintenance Manual. As a guide, system schematics are provided in this manual. Refer to the Electrical System Schematic that is located in the machine Service Manual for a complete representation of the machine that is being diagnosed.When the troubleshooting procedure instructs the service personnel to REPAIR THE HARNESS, always use the Electrical System Schematic that is located in the machine Service Manual to trace the circuit. Perform continuity checks at the connectors in order to locate the harness failures. At component connectors, always check the ground circuit. The power circuits of the control require less than 2 ohms of resistance between the ground contacts of the connector and frame ground. Signal circuits (“sensors, switches, solenoids etc.”) require less than 5 ohms of resistance for normal operation. Resistance that is greater than 5 ohms can cause incorrect diagnosing of problems. Repairs of the machine harness should be performed with the wire of the same gauge. All joints should be soldered. All joints should be taped tightly. Use the 1P-0810 Vinyl Tape or shrink sleeving for all repairs to the harness. Repairs to the data link circuit in the harness must maintain the same twist ratio in the wiring that was provided in the original harness. The two wires of the Cat Data Link must maintain a twist rate of 2 1 turns per inch. Twisting is VERY IMPORTANT! Twisting will minimize the electrical interference to other circuits that is caused by the data link. Interference to the data link from other circuits will also be minimized. During troubleshooting, inspect all component and harness connections before any component is replaced. Electrical problems can be caused if harness connections are not clean and tight. The electrical problem can be permanent or the electrical problem can be intermittent. Make sure that the connections are tight before other tests are made. The failure of an electrical component can cause the failure of one or more related components. Always attempt to find the cause of the electrical system failure and then correct the cause of the electrical system failure before replacing a component. Some machine functions that use solenoid valves require a suppressor diode across the valve coil. If the suppressor diode is faulty, electronic noise that is generated by the solenoids turning ON and OFF can cause erratic operation of the display components. If the erratic operation of the display components appears to be associated with an activity such as "blade operation", check the appropriate suppressor diode for proper operation. Data events and maintenance events are defined by the machine's configuration software. Diagnostic functions for a given event are also defined in the configuration software. The electronic control module may wait up to 30 SECONDS before displaying a system event. During troubleshooting, allow an adequate amount of time for the ECM to report that a new condition exists.