3500B and 3500B High Displacement Generator Set Engines Caterpillar

The emergency stop switch sends two signals to the engine's Electronic Control Module (ECM). The signals are used to determine if the emergency stop switch is active. The emergency stop switch is active when the switch is in the open state and the two signals are held high. The emergency stop switch is inactive when the switch is in the closed state and the two signals are held low.

If the ECM is powering up and one of the signals from the emergency stop switch is in a different state from the other signal, the ECM knows that one of the signals is faulty. If one of the signals from the emergency stop switch is in a different state from the other signal, the ECM will generate a diagnostic code that remains active until power to the ECM is cycled. The ECM will not allow the crank cycle to begin if the signals are opposite of each other. The ECM will allow the engine to be started manually in this state.

The ECM monitors the emergency stop signals at all times. If the engine is running and one of the signals from the emergency stop switch changes states, the engine will continue to run. The ECM initiates an emergency stop shutdown only when both signals are in the open state during engine operation.

For safety, the ECM will not allow the starting sequence to begin when the emergency stop switch is activated. The engine will not be able to restart until the following conditions are met.

• The engine rpm must equal zero.

• The emergency stop inputs must go low.

• The ECM has been reset.

Note: If one of the signals from the emergency stop switch is in a different state from the other signal, the Caterpillar Electronic Technician (ET) will display the warning "INVALID DATA".

Illustration 1	g01023335
Typical circuit with EMS II

Test Step 1. Check for Connector Damage.

1. Turn the ECS to the OFF position.

2. Turn the battery disconnect switch to the OFF position.

3. Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test 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 for pinch points.

Expected Result:

All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion or of pinch points.

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

  Stop.

Test Step 2. Check the ON Status of the Emergency Stop Switch.

1. Turn the circuit breaker for the battery to the ON position.

2. Connect Cat ET.

3. Turn the ECS to the SERVICE position.

4. Activate the emergency stop switch.

5. Observe the status of the emergency stop switch on Cat ET.

Expected Result:

The parameter for the emergency stop switch reads "ON".

Results:

• OK - The emergency stop switch is working correctly. Proceed to Test Step 3.

• Not OK - The parameter for the emergency stop switch does not display "ON". Proceed to Test Step 4.

Test Step 3. Check the OFF Status of the Emergency Stop Switch.

1. Deactivate the emergency stop switch.

2. Observe the status of the emergency stop switch on Cat ET.

Expected Result:

The parameter for the emergency stop switch reads "OFF".

Results:

• OK - The emergency stop switch is functioning correctly.

  Repair: The problem may be intermittent. If the problem is intermittent, refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".

  Stop.

• Not OK - The parameter for the emergency stop switch does not display "OFF". Proceed to Test Step 4.

Test Step 4. Test the Signal from the Emergency Stop Switch to the ECM.

1. Turn the ECS to the OFF position.

2. Disconnect connector P1 from the ECM. Remove wires P1-29, P1-02 and P1-24 from ECM connector P1.

3. Locate a suitable jumper wire.

4. Insert the jumper wire at P1. Connect P1-02 and P1-24 to P1-29.

5. Reconnect connector P1 to ECM connector J1.

6. Turn the ECS to the SERVICE position.

7. Observe the parameters for the emergency stop on Cat ET.

8. Turn the ECS to the OFF position.

9. Remove the jumper wire.

10. Turn the ECS to the SERVICE position.

11. Observe the parameters for the emergency stop on Cat ET.

12. Turn the ECS to the OFF position.

13. Reconnect all wires.

Expected Result:

The parameter for the emergency stop switch displays "OFF" when the jumper is installed. The parameter for the emergency stop switch displays "ON" when the jumper is removed.

Results:

• OK - The parameter on the ECM is correct. The problem is not with the ECM. Proceed to Test Step 5.

• Not OK - The parameter on the ECM is incorrect.

  Repair: Replace the ECM. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM".

  Stop.

Test Step 5. Check the Emergency Stop Switch and the Wires to the Emergency Stop Switch.

1. Turn the ECS to the OFF/RESET position.

2. Disconnect connector P1 from ECM connector J1.

3. Activate the emergency stop switch.

4. Measure the resistance between P1-11 and P1-02.

5. Measure the resistance between P1-11 and P1-24.

Expected Result:

The resistance is greater than 20,000 Ohms.

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 in the circuit of the emergency stop switch. Proceed to Test Step 7.

Test Step 6. Deactivate the Switch.

1. Deactivate the emergency shutdown switch.

2. Measure the resistance between P1-11 and P1-02.

3. Measure the resistance between P1-11 and P1-24.

Expected Result:

The resistance is less than 5 Ohms.

Results:

• OK - The resistance is less than 5 Ohms. The emergency shutdown switch and the wiring are okay.

  Repair: Reconnect all wiring and connectors and retest the system. There may have been an intermittent problem in the harness. If the problem is intermittent, refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".

  Stop.

• Not OK - The resistance is greater than 5 Ohms. There is an open circuit in the emergency shutdown switch. Proceed to Test Step 7.

Test Step 7. Check the Emergency Stop Switch.

1. Turn the ECS to the OFF position.

2. Disconnect the wires from the emergency stop switch.

3. Use a voltmeter to read the resistance across the contacts of the emergency stop switch.

4. Deactivate the emergency stop switch.

5. Measure the resistance between the contacts of the emergency stop switch.

6. Activate the emergency stop switch.

7. Measure the resistance between the contacts of the emergency stop switch.

Expected Result:

The resistance is less than 5 Ohms when the emergency stop switch is deactivated. The resistance is greater than 20,000 Ohms when the emergency stop switch is activated.

Results:

• OK - The resistance measurements are correct for both switch positions.

  Repair: The wires and/or the connectors between the emergency stop switch and the ECM connector need repair. Check the wires for continuity. Repair the connectors and/or wiring or replace the connectors and/or wiring.

  Stop.

• Not OK - The resistance measurements are incorrect for one or both switch positions.

  Repair: Replace the emergency stop switch.

  Stop.