861927T 3 Mercruiser ECM, Engine Control Module

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Schematic for the fan speed sensorTest Step 1. Inspect Electrical Connectors and Wiring
Remove the electrical power from the ECM.
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Left side engine view (typical example) (1) J1/P1 ECM connector
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Cooling fan drive assembly (2) Connector for the engine fan speed sensor (3) Cooling fan drive assembly
Thoroughly inspect connectors (1) . Also, thoroughly inspect connector (3) that is for the integral components of the fan drive assembly (4) . Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".
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P1 ECM connector (P1-4) +8 V supply (P1-5) Digital return (P1-32) Engine cooling fan speed
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 ECM connector for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".
Check the harness and the wiring for abrasion and for pinch points.Expected Result:All connectors, pins and sockets are completely coupled and inserted and the harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The harness and connectors appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem with 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 2. Check the Status of the Engine Fan Speed with Caterpillar Electronic Technician (ET)
Remove the electrical power from the ECM.
Connect Cat ET to the service tool connector. Start Cat ET.
Restore the electrical power to the ECM.
Access the "Fan Override Test" under the "Diagnostics" menu.
Start the "Fan Override Test" on Cat ET. Set the fan speed to 800 rpm.
Use a 1U-6602 Photo-Tachometer to determine the actual speed of the fan.
Compare the engine fan speed that is reported by Cat ET to the actual engine fan speed that is reported by the photo-tachometer.
Deactivate the "Fan Override Test".Expected Result:The actual fan speed is within 50 rpm of the engine fan speed that is reported by Cat ET.Results:
OK - The engine fan speed is within the desired rpm range.Repair: The sensor is operating correctly. There may be an intermittent electrical problem in a connector or in the harness. If an intermittent problem is suspected, refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - The engine fan speed is not within the desired rpm range. Proceed to Test Step 3.Test Step 3. Check the Sensor Supply Voltage at the Connector for the Engine Cooling Fan Speed Sensor
Remove the electrical power from the ECM.
Disconnect the connector for the engine cooling fan speed sensor.
Restore the electrical power to the ECM.
Measure the sensor supply voltage on the harness side of the connector for the engine cooling fan speed sensor between terminal 4 (8 V supply) and terminal 5 (digital return).Expected Result:The voltage is 8.0 0.4 VDC.Results:
OK - The voltage is 8.0 0.4 VDC. The supply voltage is reaching the sensor connector. Proceed to Test Step 4.
Not OK - The voltage is not 8.0 0.4 VDC.Repair: The supply voltage is not reaching the sensor. Refer to the diagnostic functional test Troubleshooting, "Digital Sensor Supply Circuit - Test".STOPTest Step 4. Check the Signal Frequency for the Engine Cooling Fan Speed Sensor at the Sensor Connector
Remove the electrical power from the ECM.
Remove the wire from terminal 1 (engine fan speed) on the sensor side of the connector for the engine cooling fan speed sensor. Connect the sensor connector.
Restore the electrical power to the ECM.
Access the "Fan Override Test" under the "Diagnostics" menu on Cat ET.
Start the "Fan Override Test" on Cat ET. Set the fan speed to 800 rpm.
Use a multimeter to measure the frequency between the signal wire from the sensor and engine ground.
Deactivate the "Fan Override Test".
Remove the electrical power from the ECM.
Restore all connectors and wiring to the original configuration.Expected Result:The frequency is approximately 13.3 Hz.Results:
OK - The frequency is approximately 13.3 Hz. The engine cooling fan speed sensor is generating the correct signal. Reconnect the wire to terminal 1 (engine fan speed) of the connector for the engine cooling fan speed sensor. Proceed to Test Step 5.
Not OK - The frequency is not approximately 13.3 Hz.Repair: The engine cooling fan speed sensor is not generating the correct signal. The sensor is nonserviceable. Replace the sensor. Verify that the replacement of the sensor corrects the original problem.STOPTest Step 5. Check the Signal Frequency for the Engine Cooling Fan Speed Sensor at the ECM Connector
Remove the electrical power from the ECM.
Disconnect the J1/P1 ECM connector. Remove the wire from terminal P1-32 (engine cooling fan speed sensor) at the P1 connector.
Fabricate a jumper wire that is long enough to be used in order to measure the signal frequency at the ECM connector. Crimp a connector socket to one end of the jumper wire.
Install the jumper wire into terminal location P1-32. Connect the J1/P1 connectors.
Restore the electrical power to the ECM.
Access the "Fan Override Test" under the "Diagnostics" menu on Cat ET.
Start the "Fan Override Test" on Cat ET. Set the fan speed to 800 rpm.
Measure the frequency between the jumper wire at P1-32 and engine ground.
Deactivate the "Fan Override Test".
Remove the electrical power from the ECM.
Reconnect all connectors and wires.Expected Result:The frequency is approximately 13.3 Hz.Results:
OK - The frequency is approximately 13.3 Hz.Repair: The ECM is not detecting the signal. Replace