879194148 Mercruiser PLUG

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SchematicTest Step 1. Verify That the Coolant Level is Acceptable
Ensure that the coolant level for the engine is appropriate. Refer to Operation and Maintenance Manual, "Cooling System Coolant Level - Check" for more information.Expected Result:The coolant is at an acceptable level.Results:
OK - Proceed to Test Step 2.
Not OK - Repair: Diagnose the reason for a low coolant level.Refer to the "Troubleshooting Without A Diagnostic Code" section in this manual for more information.Verify that the repair eliminates the problem. Stop.Test Step 2. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF/RESET position.
Thoroughly inspect J1/P1 ECM connector, J2/P2 ECM connector, and J47/P47 coolant flow switch connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.Expected Result:All connectors, pins, and sockets should be completely inserted and coupled. The harness and wiring should be free of corrosion, abrasion, and pinch points. All connections and grounds should be tight and free of corrosion.Results:
OK - Proceed to Test Step 3.
Not OK - Repair: Repair the circuit.Verify that the repair eliminates the problem. Stop.Test Step 3. Check Status of the Coolant Flow Switch on an Electronic Service Tool
Turn the keyswitch to the OFF/RESET position.
Connect the electronic service tool to the service tool connector.
Disconnect J47/P47 coolant flow switch connector.
Use a suitable piece of wire to short P47:1 (Coolant Flow Switch) to P47:2 (Digital Sensor Return).
Turn the keyswitch to the ON position.
Observe the status of "Engine Coolant Flow" on the electronic service tool.
Turn the keyswitch to the OFF/RESET position.Expected Result:The status should indicate "Flow" with the jumper wire in place.Results:
OK - The ECM and the wiring are operating correctly. Proceed to Test Step 4.
Not OK - Proceed to Test Step 5.Test Step 4. Check the Coolant Flow Switch
Remove the coolant flow switch from the engine.
Manually close the coolant flow switch. Ensure that excessive force is not required to close the switch.
Measure continuity between J47:1 (Coolant Flow Switch) and J47:2 (Digital Sensor Return) with the switch in the closed position.Expected Result:The switch should close easily and there should be continuity between J47:1 (Coolant Flow Switch) and J47:2 (Digital Sensor Return) with the switch in the closed position.Results:
OK - There may be a mechanical problem with the cooling system of the engine.Repair: Diagnose the cooling system of the engine. Refer to the "Troubleshooting Without a Diagnostic Code" section in this manual.Verify that the repair eliminates the problem. Stop.
Not OK - There is a problem with the coolant flow switch.Repair: Replace the coolant flow switch with a new switch.Verify that the repair eliminates the problem. Stop.Test Step 5. Check for Shorts in the Harness from the Coolant Flow Switch to the ECM
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J1/P1 ECM connector
Turn the keyswitch to the OFF/RESET position.
Disconnect the J1/P1 ECM connector.
Disconnect J47/P47 coolant flow switch connector.
Measure the resistance between P1:59 (Coolant Flow Switch) and engine ground.
Measure the resistance between P1:59 (Coolant Flow Switch) and P1:18 (Digital Sensor Return).Expected Result:The resistance should be greater than 20,000 Ohms.Results:
OK - Proceed to Test Step 6.
Not OK - There is a short between the ECM and the coolant flow switch.Repair: Repair the circuit. Stop.Test Step 6. Check for Open Circuits in the Harness from the Coolant Flow Switch to the ECM
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J1/P1 ECM connector
Turn the keyswitch to the OFF/RESET position and disconnect the J1/P1 ECM connector.
Use a suitable piece of wire to short P1:59 (Coolant Flow Switch) and P1:18 (Digital Sensor Return).
Disconnect J47/P47 coolant flow switch connector.
Measure the resistance between P47:1 (Coolant Flow Switch) and P47:2 (Digital Sensor Return).Expected Result:The resistance should be less than 10 Ohms.Results:
OK - Proceed to Test Step 7.
Not OK - There is an open circuit in the wiring harness between the coolant flow switch and the ECM.Repair: Repair the circuit.Verify that the repair eliminates the problem. Stop.Test Step 7. Check Status of the Coolant Flow Switch on an Electronic Service Tool
Turn the keyswitch to the OFF/RESET position.
Reconnect the J1/P1 ECM connector.
Disconnect J47/P47 coolant flow switch connector.
Use a suitable piece of wire to short P47:1 (Coolant Flow Switch) to P47:2 (Digital Sensor Return).
Turn the keyswitch to the ON position.
Observe the status of "Engine Coolant Flow" on the electronic service tool.
Turn the keyswitch to the OFF/RESET position.Expected Result:The status should indicate "Flow" with the jumper wire in place.Results:
OK - The ECM is responding correctly.Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent. Stop.
Not OK - The ECM is not responding correctly.Repair: Verify your results.Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM.Verify that the repair eliminates the problem. Stop.