865830T02 Mercruiser ECM, Engine Control Module

Illustration 1 g01141675
Schematic for the electrical power supply circuit
Test Step 1. Inspect the Electrical Connectors and the Wiring
Turn the keyswitch to the OFF position.
Illustration 2 g01143178
Location of the J1/P1 and J2/P2 ECM connectors (typical left side engine view)
(1) J2/P2 ECM connectors
(2) J1/P1 ECM connectors
Thoroughly inspect connectors (1) and (2). Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01218813
P1 ECM connections
(P1-48) +Battery
(P1-52) +Battery
(P1-53) +Battery
(P1-61) −Battery
(P1-63) −Battery
(P1-65) −Battery
(P1-70) Keyswitch
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the electrical power supply.
Check the torque of the allen head screws for the ECM connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and wiring for abrasions and for pinch points from the battery to the ECM. Also, check the harness and wiring for abrasions and for pinch points from the keyswitch to the ECM. Expected Result:All 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 2.
Not OK - There is a problem with the harness and/or the connectors.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.STOPTest Step 2. Check the Battery Voltage at the ECM
Disconnect the J1/P1 ECM connectors.
Turn the keyswitch to the ON position.
Measure the voltage between P1-52 (unswitched +Battery) and P1-63 (−Battery).
Measure the voltage between P1-48 (unswitched +Battery) and P1-61 (−Battery).
Measure the voltage between P1-53 (unswitched +Battery) and P1-65 (−Battery).
Measure the voltage between P1-70 (keyswitch) and P1-63 (−Battery). Expected Result:The measured voltage is between 22.0 VDC and 27.0 VDC with no suspected intermittent problems at this time.Results:
OK - The measured voltage is between 22.0 VDC and 27.0 VDC at the ECM.Repair: The ECM is receiving the correct voltage. There may be an intermittent problem in the electrical power supply circuit. If an intermittent condition is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - Battery voltage is out of range - The voltage is not between 22.0 VDC and 27.0 VDC at the ECM. The voltage is not correct at the ECM. Proceed to Test Step 3.
Not OK - Keyswitch voltage out of range - The voltage is not between 22.0 VDC and 27.0 VDC at the ECM.Repair: The voltage for the keyswitch is not correct at the ECM. Trace the wiring for the keyswitch from the ECM through the keyswitch circuit to the batteries. Also check the circuit from the keyswitch to the implement ECM of the machine. Find the problem and repair the problem. Check the circuit protection for the circuit and for the wiring. Verify that the repairs eliminate the problem.STOPTest Step 3. Check the Batteries
Measure the no-load battery voltage at the battery posts.
Load test the batteries. Use the 4C-4911 Battery Load Tester. Refer to Special Instruction, SEHS9249, "Use of 4C-4911 Battery Load Tester for 6, 8 and 12 Volt Lead Acid Batteries" and Special Instruction, SEHS7633, "Battery Test Procedure". Expected Result:The batteries pass the load test. The measured voltage is above the minimum specification for a 24V system.Results:
OK - The batteries pass the load test and the measured voltage is above the minimum specification.Repair: The batteries are OK. Check the wiring between the batteries and the ECM for a short circuit or an open circuit.Check the connectors between the batteries and the ECM for moisture and/or corrosion.Repair the wiring and/or the connectors that are suspect. Verify that the repair eliminates the problem.STOP
Not OK - The battery voltage is low or the battery did not pass the load test.Repair: Recharge or replace the faulty batteries. Verify that the repair eliminates the problem.STOP