PISTON 8J5965 - Caterpillar

Table 1
J1939 Code and Description Comments
677-3
Engine Starter Motor Relay : Voltage Above Normal The Electronic Control Module (ECM) detects a short circuit to battery positive in the high side voltage supply circuit for the starting motor relay when no start request is active.
677-4
Engine Starter Motor Relay : Voltage Below Normal The Electronic Control Module (ECM) detects A short circuit to ground in the high side voltage supply circuit for the starting motor relay.
1321-3
Engine Starter Solenoid Lockout Relay Driver Circuit: Voltage Above Normal The Electronic Control Module (ECM) detects a short circuit to battery positive on the low side (return) of the starter motor relay.
1321-4
Engine Starter Solenoid Lockout Relay Driver Circuit: Voltage Below Normal The Electronic Control Module (ECM) detects a short circuit to ground on the low side (return) of the starter motor relay
1321-5
Engine Starter Solenoid Lockout Relay Driver Circuit: Current Below Normal The Electronic Control Module (ECM) detects an open circuit on the low side (return) of the starter motor relay.
1321-12
Engine Starter Solenoid Lockout Relay Driver: Failure The Electronic Control Module (ECM) detects an over temperature condition on the output for the starting motor relay high side driver. If the code reoccurs, replace the Engine ECM. 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