89949A 1 Mercury PLATE ASSEMBLY

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Schematic for engine shutdown switchTest Step 1. Inspect the Electrical Connectors and the Wiring
Remove the electrical power from the ECM.
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(J1/P1) ECM connectors
Thoroughly inspect the J1/P1 ECM connectors and the connectors for the engine shutdown switch. Also inspect each of the machine connectors that are in the circuit. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".
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P1 ECM connector (P1-3) Sensor return (P1-41) Engine shutdown switch (N/O) (P1-40) Engine shutdown switch (N/C)
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Machine connector (Terminal 6) Sensor return (Terminal 4) Engine shutdown switch (N/C) (Terminal 5) Engine shutdown switch (N/O)
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Engine shutdown switch connector (1) Engine shutdown switch (N/C) (2) Sensor return (3) Engine shutdown switch (N/O)
Perform a 45 N (10 lb) pull test on each of the wires for the engine shutdown switch.
Check the torque of the allen head screw on the ECM connectors. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".
Check the harness and the wiring for abrasion and for pinch points from the switch back to the ECM.Expected Result:All of the 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 harness and the connectors appear to be OK. Proceed to Test Step 3.
Not OK - There is a problem with the connectors and/or wiring.Repair: Repair the wiring and/or the connectors. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the repair eliminates the problem.STOPTest Step 2. Check for Active Diagnostic Codes
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Restore the electrical power to the ECM.
Check the "Active Diagnostic Codes" screen for a 267-02 diagnostic code. Toggle the engine shutdown switch and monitor Cat ET for the active diagnostic code. Wait at least 30 seconds so that any codes may become active.
Remove the electrical power from the ECM.Expected Result:An 02 diagnostic code is not active.Results:
OK - The code does not become active.Repair: The switch is operating normally. There may be an intermittent problem in the wiring harness or in a connector. Check the wiring harness and the connectors for an intermittent electrical problem. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - An 02 diagnostic code is active. Proceed to Test Step 3.Test Step 3. Check the Resistance of the Switch Circuit at the ECM Connector
Place the engine shutdown switch in the RUN position. Ensure that the electrical power is removed from the engine ECM.
Disconnect the P1 connector.Note: Wiggle the harnesses during the following measurements in order to detect any intermittent problems.
Measure the resistance between terminals P1-3 (digital return) and P1-40 (engine shutdown switch (N/C)). The correct resistance measurement indicates a short circuit.
Measure the resistance between terminals P1-3 (return) and P1-41 (engine shutdown switch (N/O)). The correct resistance measurement indicates a open circuit.
Toggle the engine shutdown switch to the STOP position.
Measure the resistance between terminals P1-3 (return) and P1-40 (engine shutdown switch (N/C)). The correct resistance measurement indicates a open circuit.
Measure the resistance between terminals P1-3 (return) and P1-41 (engine shutdown switch (N/O)). The correct resistance measurement indicates a short circuit.
Connect the J1/P1 connectors.Expected Result:The resistance measurements are within the specifications.Results:
OK - All of the resistance measurements are within the specifications.Repair: Perform the following procedure:
Restore the electrical power to the ECM.
Use Cat ET to check for the active 267-02 code again. Toggle the engine shutdown switch and check for the code. Also, wiggle the switch harness from the switch to the ECM in order to reveal an intermittent problem.If the code does not recur, the problem is resolved. The original problem was probably caused by a poor electrical connection.If the code recurs, the ECM is not detecting the switch inputs correctly. Replace the ECM. Refer to electronic troubleshooting Troubleshooting, "Replacing the ECM".STOP
Not OK - At least one of the resistance measurements is not within specifications. There is a problem in the switch or in a harness. Proceed to Test Step 4.Test Step 4. Check the Operation of the Engine Shutdown Switch
Disconnect the connectors for the engine shutdown switch.
Place the engine shutdown switch in the RUN position.
Measure the resistance between terminals 2 (return) and 3 (engine shutdown switch (N/O)). The correct resistance measurement indicates an open circuit.
Measure the resistance between terminals 1 (engine shutdown switch (N/C)) and 2 (return). The correct resistance measurement indicates a short circuit.
Toggle the engine shutdown switch to the STOP position.
Measure the resistance between 1 (engine shutdown switch (N/C)) and 2 (return). The correct resistance measurement indicates an open circuit.
Measure the resistance between 2 (return) and 1 (engine shutdown switch (N/O)). The correct resistance measurement indicates a short circuit.Expected Result:The resistance measurements are within the specifications.Results:
OK - All of the resistance measurements are within the specifications.Repair: The switch is OK. There is a problem in the wiring harness or the connectors. Check the machine wiring harnesses and the connectors for an open circuit or a short circuit. Repair the wiring and/or the connectors. Replace parts, if necessary. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - At least one of the resistance measurements is not within speci