75586 Mercruiser BALANCER, HARMONIC - CRANKSHAFT

When the keyswitch is turned to the START position, a signal is sent to pin P1:63 on the engine ECM. Power is supplied from P1:19 to the starting motor relay.The starting motor relay supplies battery power to the starting solenoid attached to the starting motor. The ECM monitors starting circuit health on both the high and low side of the starting motor relay and will detect and report any abnormal conditions.A starting motor relay output override is available through Cat® Electronic Technician (ET) to manually activate the ECM output to the starting motor relay.
Table 2
Troubleshooting Test Steps Values Results
1. Check for Codes
A. Turn the keyswitch to the ON position.
B. Connect the electronic service tool to the diagnostic connector.
C. Make a note of any active diagnostic codes.
Codes
Result: Diagnostic code 677-3, 677-4 or 1321-4 diagnostic code is active or logged.
Proceed to Test Step 2.
Result:Diagnostic code 1321-3 is active.
Proceed to Test Step 3.
Result:A 1321-5 diagnostic code is active or logged.
Proceed to test Step 4.
2. Check for a Short to Battery Positive or Short to Ground
A. Turn the keyswitch to the OFF position
B. Unplug the connector for the starter motor relay.
C. Turn the keyswitch to the ON position.
D. Observe status of active diagnostic code 677-3, 677-4, or 1321-4.
Codes
Result: Diagnostic code 677-3 remains active.
Repair: There is a short to a positive voltage on the high side supply wire in between the engine ECM and the connector for the starting motor relay. Repair or replace the wiring harness.
Result:Diagnostic code 677-3 is no longer active and is now logged.
Repair: The starting motor relay was shorted to a positive power source. Replace the starting motor relay.
Result: Diagnostic code 677-4 remains active.
Repair: There is a short to ground on the high side supply wire in between the engine ECM and the connector for the starting motor relay. Repair or replace the wiring harness.
Result: Diagnostic code 677-4 is no longer active and is now logged.
Repair: The starting motor relay was shorted to ground. Replace the starting motor relay.
Result: Diagnostic code 1321-4 is no longer active. Diagnostic code 1321-5 is now active.
Repair: The starting motor relay was shorted to ground. Replace the starting motor relay.
Result: Diagnostic code 1321-4 remained active with the starting motor relay disconnected.
Repair: There is a short to ground on the low side (return) wire in between the connector for the starting motor relay and the ECM. Repair or replace the wiring harness.
3. Check for a Short to a Battery Positive Voltage Source
A. Turn the keyswitch to the OFF position.
B. Unplug the connector for the starting motor relay.
C. Turn the keyswitch to the ON position.
D. Use a multi-meter to measure for a positive voltage between the following locations:
Terminal 2 of the starting motor relay connector and engine ground.
Short
Result: Battery voltage was measured between Terminal 2 of the starting motor relay connector and engine ground.
Repair: There is a short to a positive voltage source on the low side (return) wire in between the starting motor relay connector terminal 2 and the engine ECM. Repair or replace the wiring harness.
Result: Battery voltage is not present on the low side (return) wire with the relay disconnected.
Repair: The starting motor relay is internally shorted to a power source. Replace the starting motor relay.
4. Check for an Open Circuit
A. Turn the keyswitch to the OFF position.
B. Disconnect the connector for the starting motor relay.
C. Install a jumper wire to create a short circuit between terminals 2 and 5 on the connector for the starting motor relay.
D. Turn the keyswitch to the ON position.
Open
Result: Diagnostic code 1321-5 is now logged and 677-4 is now active.
Repair: Replace the starting motor relay.
Result: Diagnostic code 1321-5 remains active with the jumper wire in place.
Repair: There is an open circuit on the low side (return) wire in between the connector for the starting motor relay and the engine ECM. Repair or replace the wiring harness.
If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).