3500B Locomotive Engines Caterpillar

The ECM receives two signals from the Start/Stop Switch. A redundant signal is provided to the ECM in order to determine if the Start/Stop Switch is active.

The switch is in the STOP position, when both of the signals to the ECM are high.

The switch is in the START position when both of the signals to the ECM are low.

If two different signals are detected during the powerup, the ECM will determine that one of the signals is incorrect. A diagnostic code will be logged and a diagnostic code will remain active.

The engine will continue to run when the ECM detects two different signals. If both of the signals are open, the engine will stop.

The Start/Stop Switch can be included in the engine start system. The ECM will begin the engine start sequence, when the contacts close and the engine is not running.

Refer to the "Locomotive Manuals" for more information.

Illustration 1	g00850675

Test Step 1. Check for Connector Damage.

1. Turn the engine control to the OFF position.

2. Turn the breaker at the battery to the OFF position.

3. Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.

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

5. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

6. Check the customer connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).

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

Expected Result:

The connectors and wiring should be free of the following problems: damage, corrosion, abrasion and incorrect attachment.

Results:

• OK - The connectors and wiring are okay. Proceed to test step 2.

• Not OK - The connectors and/or wiring need repair.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring.

  Stop.

Test Step 2. Check the Status of the Start/Stop Switch on the ET.

1. Activate one of the Start/Stop Switches. Be sure that none of the other switches have been activated.

2. Connect the ET to the service tool connector.

3. Connect the main power.

4. Monitor the parameter for the switch on the ET.

Expected Result:

The parameter for the switch should read "ON".

Results:

• OK - The parameter for the switch reads "ON". Proceed to test step 3.

• Not OK - The parameter for the switch does not read "ON". Proceed to test step 4.

Test Step 3. Check the Status of the Start/Stop Switch on ET.

1. Deactivate all the Start/Stop Switches.

2. Observe the status of the Start/Stop Switch on the Electronic Service Tool.

Expected Result:

The parameter for the switch should read "OFF".

Results:

• OK - The parameter for the switch reads "OFF".

  Repair: The switch is functioning correctly.

  Stop.

• Not OK - The parameter does not display "OFF". Proceed to test step 4.

Test Step 4. Check the Start/Stop Switches and the Harness Wiring for an Open Circuit.

1. Disconnect the main power.

2. Disconnect the ECM connector J1/P1.

3. Activate one of the Start/Stop Switches. Be sure that all other switches are not active.

4. Measure the resistance between P1-29 and P1-8.

5. Measure the resistance between P1-29 and P1-14.

6. Deactivate the Start/Stop Switch.

7. Check the next Start/Stop Switch. Continue this process for all of the Start/Stop Switches.

8. Reconnect all connectors.

Expected Result:

The resistance should read less than 10 Ohms.

Results:

• OK - The resistance is less than 10 Ohms. Proceed to test step 5.

• Not OK - The resistance is greater than 10 Ohms.

  Repair: There is an open or excessive resistance in the harness or the Start/Stop Switch. Check continuity through the harness. Check the Start/Stop Switch for proper operation. Repair the connectors or wiring and/or replace the connectors or wiring. If necessary, replace the Start/Stop Switch.

  Stop.

Test Step 5. Check the Start/Stop Switches and the Harness Wiring for a Short Circuit.

1. Disconnect the main power.

2. Disconnect the ECM connector J1/P1.

3. Deactivate all of the Start/Stop Switches.

4. Measure the resistance between P1-29 and P1-8.

5. Measure the resistance between P1-29 and P1-14.

6. Reconnect all connectors.

Expected Result:

The resistance should be greater than 20,000 Ohms when the Start/Stop Switches are deactivated.

Results:

• OK - The resistance is greater than 20,000 Ohms. Proceed to test step 6.

• Not OK - The resistance is less than 20,000 Ohms. There is a short circuit in one of the switches.

  Repair: There is a short in the harness or the Start/Stop Switch. Check continuity through the harness. Check the Start/Stop Switch for proper operation. Repair the connectors or wiring and/or replace the connectors or wiring. If necessary, replace the Start/Stop Switch. Verify that the problem is no longer present.

  Stop.

Test Step 6. Check the ECM.

1. Disconnect the main power.

2. Disconnect J1/P1.

3. Remove wire F717-YL from ECM connector P1-14. Install a wire jumper into the socket for P1-14.

4. Remove wire F716-WH from ECM connector P1-08. Install a wire jumper into the socket for P1-08.

5. Remove wire 998-BR from ECM connector P1-29. Install a wire jumper into the socket for P1-29.

6. Connect ECM connector J1/P1.

7. Connect the wire jumpers in P1-14 and P1-08 to the wire jumper in P1-29.

8. Connect the main power.

9. Observe the parameter for the switch on the ET.

10. Remove the wire jumpers.

11. Observe the parameter for the switch on the ET.

12. Disconnect the main power. Remove the wire jumpers. Reinstall all wires, and reconnect J1/P1.

Expected Result:

The status of the Start/Stop Switch should read "ON" when the short is in place. The status of the Start/Stop Switch should read "OFF" when the short is removed.

Results:

• OK - The parameter for the Start/Stop Switch is displaying the proper states. The problem is not with the ECM.

  Repair: Replace all wires and connectors. Check the system for proper operation. The problem may be intermittent. If the problem is intermittent refer to Troubleshooting, "Inspecting Electrical Connectors".

  Stop.

• Not OK - The parameter for the Start/Stop Switch does not show the correct states.

  Repair: The ECM is not reading the inputs correctly. Replace the ECM. Refer to Troubleshooting, "Replacing the ECM".

  Stop.