Switch circuits may have problems such as faulty wiring, faulty switches, or faulty connectors. Use the following diagnostic procedures in order to diagnose problems with these switch circuits and repair these switch circuits:
- Droop-isochronous switch
- Event reset switch
- Low idle switch
- Maintenance clear switch
- Monitoring system override
- Remote engine stop switch
- Run/stop switch
These switches are normally open or normally closed.
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| Illustration 1 | g01366881 |
Typical switch inputs and wiring | |
Test Step 1. Check the Electrical Connectors and the Wiring
- Remove the electrical power from the Electronic Control Module (ECM).
- Thoroughly inspect the connections for the suspect switch. Refer to Troubleshooting, "Electrical Connectors - Inspect".
- Perform a 45 N (10 lb) pull test on each of the wires in the circuit for the suspect switch.
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| Illustration 2 | g01560517 |
Terminal locations at the J1/P1 ECM connectors that are for the switch circuits (P1-22) Remote engine stop switch (P1-23) Maintenance clear switch (P1-46) Monitoring system override (P1-47) Run/stop switch (P1-56) Event reset switch (P1-58) Low idle switch (P1-60) Droop-isochronous switch | |
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| Illustration 3 | g01560534 |
Terminals at the engine interface connector that are for the switch circuits (Terminal 36) Remote engine stop switch (Terminal 39) Maintenance clear switch (Terminal 47) Monitoring system override (Terminal 67) Run/stop switch (Terminal 68) Event reset switch (Terminal 69) Low idle switch (Terminal 70) Droop-isochronous switch | |
- Check the allen head screw on each ECM connector for the proper torque. Also, check the allen head screw on the customer connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
- Check the harness and wiring for abrasions and for pinch points from the battery to the ECM.
Expected Result:
All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion and of pinch points.
Results:
- OK - The wiring and connectors appear to be OK. Proceed to Test Step 2.
- Not OK - There is a problem with the wiring and/or a connector.
Repair: Repair the wiring and/or the connector. Replace parts, if necessary. Ensure that all of the seals are properly connected. Verify that the repair eliminates the problem.
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Test Step 2. Test the Switch for Proper Operation
- Disconnect the P1 connector.
- Refer to Table 1. Determine the P1 terminal for the suspect switch.
Show/hide table
Table 1 Terminals for the Switch Inputs Name of the Switch Terminal Locations at the J1/P1 ECM Connectors Terminal Locations at the Engine Interface Connector Droop-isochronous switch 60 70 Event reset switch 56 68 Low idle switch 58 69 Maintenance clear switch 23 39 Monitoring system override switch 46 47 Remote engine stop switch 22 36 Run/stop switch 47 67
- Connect one lead of a multimeter to the P1 terminal for the suspect switch. Connect the other lead of the multimeter to negative ground.
- Measure the resistance between the P1 terminal for the suspect switch and negative ground.
Note: Wiggle the harnesses during the following measurements in order to reveal any intermittent short condition.
- Activate the switch and measure the resistance again.
Expected Result:
One resistance measurement indicates an open circuit. The other resistance measurement indicates that a short circuit exists.
Results:
- OK - One resistance measurement indicates an open circuit. The other resistance measurement indicates that a short circuit exists.
Repair: The switch is operating correctly. The wiring does not have a short circuit or an open circuit. Operate the engine and check the switch for proper operation.If the switch does not operate correctly, there may be a short circuit between the circuit for the suspect switch and another circuit. Carefully reinspect the components. Refer to Troubleshooting, "Electrical Connectors - Inspect". Locate the short circuit and perform repairs.
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- Not OK - Both resistance measurements indicate an open circuit or both resistance measurements indicate a short circuit.
Repair: There is a problem with the circuit for the switch. The problem could be in the switch, in the wiring, or in a connector.Carefully reinspect the components. Refer to Troubleshooting, "Electrical Connectors - Inspect" for information that relates to troubleshooting suspect electrical problems in the harness.If the inspection does not identify the faulty component, replace the switch and test the switch again.If the problem is not resolved, repair the wiring or the connector. Replace parts, if necessary. Verify that the problem is resolved.
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