PLATE-SEAL 3572646 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with power to the Electronic Control Module (ECM). Also use this procedure if either of the diagnostic codes in Table 1 are active or easily repeated.
Table 1
Diagnostic Trouble Codes
J1939 Code and Description Conditions that Generate the Code System Response
168-3 Battery Potential / Power Input #1 : Voltage Above Normal The ECM detects voltage that is above the acceptable value. The code is logged.
168-4 Battery Potential / Power Input #1 : Voltage Below Normal The ECM detects voltage that is above the acceptable value. The code is logged. The engine ECM requires the keyswitch to be in the ON position in order to maintain communications with Caterpillar Electronic Technician (ET).This procedure tests whether proper voltage is being supplied to the ECM.The ECM is continuously powered with +Battery voltage that is supplied to inputs P1-48, P1-52, P1-53, P1-55, and P1-57 and P1-70 (keyswitch). If an emergency stop is initiated, the ECM relay will be energized and battery voltage will be removed from the ECM.Power to the ECM is provided by a set of normally closed contacts that are in the ECM relay. The ECM relay is controlled by a set of normally open contacts in the emergency stop switch. When the emergency stop switch is placed in the STOP position, the contacts in the emergency stop switch are closed. +24 VDC is then supplied to the control circuit for the ECM relay. The contacts in the relay are opened and power is removed from the ECM.Opening the battery disconnect switch will also remove power from the ECM. Place the battery disconnect switch in the OFF position. The ground connection to inputs P1-61, P1-63, P1-65, P1-67, and P1-69 of the ECM will be removed.During an engine start sequence, the Starting Motor Magnetic Switch (SMMS) is used by the ECM to engage the starting motor. Voltage for the control solenoid for the SMMS is supplied by the ECM. When the ECM supplies the signal, the SMMS is energized. This powers the starting solenoid and the starter is engaged.Circuit protection is provided by circuit breakers for the ECM relay, the SMMS, and the emergency stop switch.
Illustration 1 g02666357
Schematic for the electrical power supply (typical example)
Test Step 1. Inspect the Electrical Connectors and the Wiring
Turn the main disconnect switch to the OFF position.
Illustration 2 g02721290
Location of the J1/P1 and the J2/P2 ECM connectors (typical engine view)
(1) J1/P1 ECM connector
(2) J2/P2 ECM connector
Thoroughly inspect connectors (1) and (2). Also, thoroughly inspect any other connectors that are associated with the circuit. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g02725420
P2 ECM connector
(P2-51) + SMMS
(P2-43) Return
(P2-59) + SMMS
(P2-60) Return
Illustration 4 g01206554
P1 ECM connector
(P1-48) +Battery
(P1-52) +Battery
(P1-53) +Battery
(P1-55) +Battery
(P1-57) +Battery
(P1-61) −Battery
(P1-63) −Battery
(P1-65) −Battery
(P1-67) −Battery
(P1-69) −Battery
(P1-70) Keyswitch
Illustration 5 g02761236
Engine interface connector
(Terminal 36) Return
(Terminal 40) Return
(Terminal 48) +Battery
(Terminal 52) +Battery
(Terminal 54) Emergency shutdown
(Terminal 70) Keyswitch
Illustration 6 g02761237
Power interface connector
(Terminal 4) +Battery
(Terminal 5) +Battery
(Terminal 6) −Battery
(Terminal 7) −Battery
(Terminal 29) Return
(Terminal 30) Return
(Terminal 61) Emergency shutdown
Illustration 7 g01207940
Terminal