5220181KZ Mercruiser END MODEL, +STERN DRIVE BRVII (1.81:1 Ratio)

Illustration 1 g01177676
Schematic for the coolant flow switch
Test Step 1. Verify that the Coolant Level is Correct
Ensure that the coolant level for the engine is correct. 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 - The coolant is at an acceptable level. Proceed to Test Step 2.
Not OK - The coolant is low.Repair: Diagnose the reason for a low coolant level.Refer to Systems Operation/Testing and Adjusting, "Cooling System" for more information.Verify that the repair eliminates the problem.STOPTest Step 2. Inspect the Electrical Connectors and the Wiring
Turn the keyswitch to the OFF position.
Illustration 2 g01144470
Thoroughly inspect connectors (1). Also, thoroughly inspect any connectors that are associated with the coolant flow switch. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01139422
P1 ECM connector
(P1-18) Sensor return
(P1-45) Coolant flow switch
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and the wiring for abrasion and for pinch points. Expected Result:All connectors, pins, and sockets are completely inserted and coupled. The harness and wiring are free of corrosion, of abrasion, and of pinch points. All connections and grounds are tight and free of corrosion.Results:
OK - The harness and wiring appear to be OK. Proceed to Test Step 3.
Not OK - There is a problem in the connectors and/or wiring.Repair: Repair the connectors or wiring and/or replace the connectors or wiring. 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 3. Check the Status of the Coolant Flow on the Caterpillar Electronic Technician (ET)
Turn the keyswitch to the OFF position.
Connect Cat ET to the service tool connector.
Observe the reading for coolant flow on the Cat ET.
Turn the keyswitch to the START position. Start the engine.
Observe the reading for coolant flow on the Cat ET.
Turn OFF the power to the ECM. Expected Result:The Cat ET indicates "NO FLOW" while the engine is not running. The Cat ET indicates "FLOW" while the engine is running.Results:
OK - Cat ET indicates "NO FLOW" while the engine is not running. Cat ET indicates "FLOW" while the engine is running. The switch is OK.Repair: If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - Cat ET does not indicate "NO FLOW" while the engine is not running. Cat ET does not indicate "FLOW" while the engine is running. Cat ET does not indicate the correct status of the coolant flow switch. Proceed to test step 4.Test Step 4. Create a Short Circuit at the Connector of the Coolant Flow Switch
Turn the keyswitch to the OFF position.
Connect Cat ET to the service tool connector.
Disconnect the connector at the coolant flow switch.
Use a suitable piece of wire to short the terminals on the harness side of the coolant flow switch.
Turn the keyswitch to the ON position.
Observe the status of "Engine Coolant Flow" on Cat ET.
Turn the keyswitch to the OFF position. Expected Result:The status indicates "Flow" with the jumper wire in place.Results:
OK - The ECM and the wiring are operating correctly. Proceed to Test Step 5.
Not OK - The status indicates "NO FLOW". Proceed to Test Step 6.Test Step 5. Check the Continuity of the Coolant Flow Switch
Pressurized System: Hot coolant can cause serious burns. To open the cooling system filler cap, stop the engine and wait until the cooling system components are cool. Loosen the cooling system pressure cap slowly in order to relieve the pressure.
Drain the engine coolant below 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 terminals at the coolant flow switch while the switch is in the closed position. Expected Result:The switch closes easily and there is continuity between terminals 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 Systems Operation/Testing and Adjusting, "Cooling System".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.STOPTest Step 6. Check the ECM
Fabricate a jumper wire that is long enough to reach from the P1 ECM connector to the engine ground stud. Crimp a socket terminal to one end of the jumper wire.
Disconnect the J1/P1 ECM connector.
Remove the wire from terminal P1-44 at the ECM connector. Install the socket terminal of the jumper wire into P1-44.
Connect the J1/P1 ECM connector.
Short the jumper wire in P1-44 to the engine ground stud.
Turn the keyswitch to the ON position.
Observe the status of "Engine Coolant Flow" on Cat ET.
Turn the keyswitch to the OFF position. Expected Result:The status indicates "Flow" with the jumper wire in place.Results:
OK - The status indicates "Flow" with the jumper wire in place.Repair: There is an open circuit in the harness between the coolant flow switch and the ECM. Repair the harness or replace the harness.STOP
Not OK - The status indicates "NO FLOW".Repair: The ECM is responding correctly. Verify your results. Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM. Verify that the repair eliminates the problem.STOP