This switch circuit may have problems such as faulty connectors, faulty wiring, or a problem with the switch. Use the following diagnostic procedure in order to diagnose and repair a problem with the switch circuit.
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| Illustration 1 | g02368336 |
Schematic for the idle/rated speed switch | |
When the switch is in the "IDLE" position, the circuit is open. When the switch is in the "RATED" position, a ground signal is supplied to the J1-28 input of the ECM.
Test Step 1. Check the Electrical Connectors and the Wiring
- Set the engine control to the OFF/RESET position. Remove the electrical power from the engine.
- Thoroughly inspect connectors (1) and (3). Thoroughly inspect the connections for the suspect switch. Refer to Troubleshooting, "Inspecting Electrical Connectors".
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| Illustration 2 | g01393766 |
Location of the ECM connectors that are related to the engine speed switch circuit (typical left front engine view) (1) J1/P1 ECM connector | |
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| Illustration 3 | g01393423 |
Location of the connectors that are for the engine speed switch (typical left rear engine view) (2) Interface box (3) Engine interface connector (40 pin) | |
- 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 4 | g02652899 |
Terminal locations at the J1/P1 ECM connectors that are for the engine speed switch (P1-28) Idle/rated speed (P1-31) Digital return | |
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| Illustration 5 | g02652985 |
Terminal locations at the engine interface connector that are for the engine speed switch (P1-18) Digital return (P1-22) Idle/rated speed | |
- Check the allen head screw on each ECM connector and the customer connector. Refer to Troubleshooting, "Inspecting Electrical Connectors" for the correct torque value.
- 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 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 are 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.
- Use a multimeter to check the resistance of the switch circuits. Insert one lead of multimeter into terminal location P1-28. Insert the other lead of the multimeter into terminal location P1-31.
- Measure the resistance between the P1 terminal for the suspect switch and engine 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 continuity in the circuit.
Results:
- OK - One resistance measurement indicates an open circuit. The other resistance measurement indicates continuity.
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 make repairs.
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- Not OK - Both resistance measurements indicate an open circuit or both resistance measurements indicate a short circuit. There is a problem with the circuit for the switch.
Repair: The problem could be in the switch, in the wiring, or in a connector.Carefully reinspect the components. Refer to Troubleshooting, "Electrical Connectors - Inspect".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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