3500B and 3500C Locomotive Engines Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the power to the engine's Electronic Control Module (ECM) or if any one of the diagnostic codes in Table 1 is active or easily repeated. Refer to Troubleshooting, "Event Code List" for the default conditions for event codes.

To reduce resistance in the wiring harness, there are two isolated power connections to the ECM. The connections must be complete in order to ensure proper engine operation. There may always be a constant power supply to the ECM when the locomotive engine is shutdown. In order to shut off the power to the ECM, the breaker for the ECM must be turned to the OFF position or the battery power needs to be disconnected.

The engine will begin the start-up when the following conditions exist:

• The ECM detects the input voltage at the input for the keyswitch.

• The emergency stop switch is not activated.

• The start/run/stop switch is in the RUN position.

Note: Use an isolation transformer between the battery and the ECM in order to protect the ECM against a voltage spike or a ground loop.

An emergency stop push button and a start/run/stop switch are provided in the junction box.

The customer can install multiple start/run/stop switches(push button) and emergency stop push buttons. When the start/run/stop switches are activated the inputs to the ECM from the start/run/stop switches go low.

When the emergency stop push button is activated, the emergency stop inputs float high. The fuel supply to the injectors will be cut off and the air shutoff relays will be activated.

Illustration 1	g01314139
Typical schematic

Illustration 2	g01258369
P1 ECM connector (P1-52) +Battery (P1-53) +Battery (P1-63) −Battery (P1-65) −Battery (P1-70) "ECM reset switch" (Keyswitch)

Illustration 3	g01258374
Connector "A" (Terminal 7) +Battery (Terminal 9) +Battery (Terminal 11) −Battery (Terminal 13) −Battery

Illustration 4	g01258377
Connector "B" (Terminal 13) "ECM reset switch" (Keyswitch)

Illustration 5	g01258378
Connector "F" (Terminal 2) −Battery (Terminal 6) +Battery

Illustration 6	g01234146
Location of ECM connectors

Test Step 1. INSPECT ELECTRICAL CONNECTORS AND WIRING

1. Turn the breaker for the ECM to the OFF position.

2. Thoroughly inspect the ECM connectors J1/P1. Inspect all of the other connectors in the circuit. Refer to Troubleshooting, "Inspecting Electrical Connectors" for the proper procedure for inspecting system wiring.

3. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.

4. Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.

5. Check the harness and the wiring for abrasion and for pinch points.

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 harness and wiring are OK. Proceed to Test Step 2.

• Not OK - There is a problem in the connectors and/or wiring.

  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.

  Verify that the repair eliminates the problem.

  STOP

Test Step 2. CHECK THE BATTERY VOLTAGE

1. Measure no-load voltage at the battery posts. Refer to Systems Operation/Testing and Adjusting for the proper procedures to check the batteries.

2. Load test the batteries. Use the 4C-4911 Battery Load Tester. Refer to the Operating Manual, SEHS9249. Refer to Special Instruction, SEHS7633.

Expected Result:

The no-load voltage at the batteries is at least 23.5 VDC, and the batteries pass the load test.

Results:

• OK - The no-load voltage at the batteries is at least 23.5 VDC, and the batteries pass the load test. Proceed to Test Step 3.

• Not OK - The no-load voltage at the batteries is less than 23.5 VDC, and/or the batteries fail the load test.

  Repair: The batteries or the alternator are causing the problem. Recharge the batteries or replace the batteries. Verify that the original condition is resolved. Refer to Systems Operation/Testing and Adjusting for information on the charging system.

  STOP

Test Step 3. CHECK THE VOLTAGE AT THE ECM CONNECTOR

1. Disconnect the J1/P1 ECM connector.

2. Turn the breaker for the ECM to the ON position.

3. Wiggle the harness during the following test steps in order to find an intermittent condition.

   1. Measure the voltage between P1-52 (positive battery) and P1-63 (negative battery).

   2. Measure the voltage between P1-53 (positive battery) and P1-65 (negative battery).

   3. Measure the voltage between P1-70 (ECM reset) and P1-65 (negative battery).

4. Turn the breaker for the ECM to the OFF position.

Expected Result:

The voltage is ± 1 VDC from the voltage at the battery terminals.

Results:

• OK - The ECM is receiving the correct voltage.

  Repair: If an intermittent condition is suspected, refer to Troubleshooting, "Inspecting Electrical Connectors".

  STOP

• Not OK - The voltage is not ± 1 VDC from the voltage at the battery terminals. Proceed to Test Step 4.

Test Step 4. CHECK THE VOLTAGE FROM THE REMOTE JUNCTION BOX

1. Disconnect connector A and connector B at the remote junction box. Refer to Illustration 1 in order to identify the configuration of the wiring.

2. Turn the breaker for the ECM to the ON position.

3. Wiggle the harness during the following test steps in order to find an intermittent condition.

   1. Measure the voltage between Terminal 07 (positive battery) and Terminal 11 (negative battery) on connector A.

   2. Measure the voltage between Terminal 09 (positive battery) and Terminal 13 (negative battery) on connector A.

   3. Measure the voltage between Terminal 13 (ECM reset) and Terminal 65 (negative battery) on connector A and B.

4. Turn the breaker for the ECM to the OFF position.

Expected Result:

The voltage is ± 1 VDC from the voltage at the battery terminals.

Results:

• OK - The voltage is correct at the connectors from the remote junction box to the ECM.

  Repair: The problem is in the wiring and/or connectors between the connector on the remote junction box and the ECM. Use continuity checks in order to find the open or short in the circuitry.

  STOP

• Not OK - The voltage is not ± 1 VDC from the voltage at the battery terminals. Proceed to Test Step 5.

Test Step 5. CHECK THE VOLTAGE TO THE REMOTE JUNCTION BOX

1. Disconnect connector F at the remote junction box.

2. Turn the breaker for the ECM to the ON position.

3. Wiggle the harness during the following test steps in order to find an intermittent condition.

4. Measure the voltage between terminal 2 and terminal 6 on the side of connector F that goes to the isolation transformer.

Expected Result:

The voltage is ± 1 VDC from the voltage at the battery terminals.

Results:

• OK - The voltage is correct to the remote junction box.

  Repair: The problem is in the wiring and/or connectors between connector F on the remote junction box and connector A or connector B in the remote junction box. Use continuity checks in order to find the open or short in the circuitry. Repair the connectors or wiring and/or replace the connectors or wiring in the remote junction box.

  STOP

• Not OK - The voltage is not ± 1 VDC from the voltage at the battery terminals. The voltage is not correct at the connector on the remote junction box.

  Repair: Verify that the breaker for the ECM is not tripped. Repair the connectors or wiring and/or replace the connectors or wiring between the remote junction box and the isolation transformer.

  .

  STOP