861925T 3 Mercruiser ECM, Engine Control Module

Illustration 1 g01148488
Schematic for the engine temperature sensors
Test Step 1. Inspect the Electrical Connectors and the Wiring
Remove the electrical power from the ECM.
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Typical left side view
(1) Engine coolant temperature sensor
(2) Intake manifold air temperature sensor
(3) J2/P2 ECM connector
Thoroughly inspect connectors (3). Inspect the sensor connectors. Refer to diagnostic functional tests Troubleshooting, "Electrical Connectors - Inspect".
Illustration 3 g01223463
P2 terminations for the engine temperature sensors
(P2-13) Engine coolant temperature
(P2-30) Return
(P2-56) Intake manifold air temperature
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Harness connector for the temperature sensors
(1) Signal
(2) Return
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the temperature sensors.
Check the torque of the allen head screws for the ECM connectors. Refer to diagnostic functional tests Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and wiring for abrasions and for pinch points from each sensor to the ECM. Expected Result:All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The connectors and wiring are OK. Proceed to Test Step 2.
Not OK - There is a problem in 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 the Caterpillar Electronic Technician (ET) to the service tool connector. Refer to electronic troubleshooting Troubleshooting, "Electronic Service Tools".
Restore the electrical power to the ECM.
Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
Look for an 03 diagnostic code or an 04 diagnostic code. Expected Result:No diagnostic codes are active.Results:
OK - No diagnostic codes are active.Repair: The problem may have been related to a faulty connection in the harness. Carefully reinspect the connectors and wiring. Refer to diagnostic functional tests Troubleshooting, "Electrical Connectors - Inspect" for additional information.STOP
Not OK - An 04 diagnostic code is active at this time. Proceed to Test Step 3.
Not OK - An 03 diagnostic code is active at this time. Proceed to Test Step 4.Test Step 3. Disconnect the Suspect Sensor in Order to Create an Open Circuit
Remove the electrical power from the ECM.
Disconnect the suspect sensor from the engine harness.
Restore the electrical power to the ECM. Wait at least 30 seconds for activation of the diagnostic codes.
Access the "Active Diagnostic Codes" screen on Cat ET and check for an active 03 diagnostic code for the suspect sensor.
Remove the electrical power from the ECM. Expected Result:An 03 diagnostic code is now active for the suspect sensor.Results:
OK - An 04 diagnostic code was active before disconnecting the sensor. An 03 diagnostic code became active after the sensor was disconnected. The harness and the ECM are OK. There may be a problem with the sensor.Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.Verify that the repair eliminates the problem.STOP
Not OK - The 04 diagnostic code is still present. Leave the sensor disconnected. There is a problem with the harness or with the ECM. Proceed to Test Step 7.Test Step 4. Check the Pull-up Voltage at the Sensor Connector
Remove the electrical power from the ECM.
Disconnect the suspect sensor at the sensor connector.
Restore the electrical power to the ECM.
Measure the voltage between terminals 1 (Signal) and 2 (Return) at the harness connector.
Remove the electrical power from the ECM. Expected Result:The voltage is 5.5 0.5 VDC.Results:
OK - The voltage is 5.5 0.5 VDC. The correct pull-up voltage is present at the harness connector for the suspect sensor.Repair: The open circuit is in the sensor or the wire between the sensor and the sensor connector. Replace the sensor. Do not install the sensor in the engine. Verify that no diagnostic codes are active for the suspect sensor before permanently installing the sensor.STOP
Not OK - The voltage is not 5.5 0.5 VDC. Proceed to Test Step 5.Test Step 5. Check the Signal Wire for a Short Circuit
Remove the electrical power from the ECM.
Disconnect the P1 and P2 connectors.
Measure the resistance between the terminal for the suspect sensor's signal wire at the ECM connector and all of the remaining terminals on the P2 connector.
Measure the resistance between the terminal for the suspect sensor's signal wire at the ECM connector and all of the remaining terminals on the P1 connector.
Measure the resistance between the terminal for the suspect sensor's signal wire at the ECM connector and the engine ground.
Connect the J1/P1 and J2/P2 connectors. Expected Result:Each check of the resistance indicates an open circuit.Results:
OK - Each check of the resistance indicates an open circuit. Proceed to Test Step 6.
Not OK - At least one check of the resistance does not indicate an open circuit. There is a problem with the wiring. There may be a problem with a connector.Repair: Repair the wiring and/or the connectors. Replac