3500B Marine Engines Caterpillar

The Secondary Electronic Control Module (ECM) has the ability to stop the engine by cutting off the air supply in an emergency situation. The ECM activates the air shutoff relays which energize the two air shutoff solenoids. The solenoids trip the air shutoff valves.

There are two conditions which cause the engine control to activate the air shutoff relay. The first condition occurs when the operator initiates a remote shutdown. When the remote emergency stop button is activated, the engine shutdown inputs to the primary ECM and the secondary ECM go high. The secondary ECM will recognize this change. The secondary ECM will energize the output for the air shutoff solenoids. The "emergency stop lockout relay" is energized by the output for the air shutoff. Voltage from the "control switch breaker" comes through the ECS and the "emergency stop lockout relay" in order to energize the emergency stop relay. Voltage from pin 1 of the emergency stop switch goes to the emergency stop relay. When the emergency stop relay is energized the voltage goes through the normally open contacts of the relay. The voltage from the emergency stop relay energizes the air shutoff relays. The air shutoff relays energize. The normally open contacts of the relay close. Voltage from the "relay breaker" energizes the air shutoff solenoids.

At the same time, the primary ECM relay and the secondary ECM relay will de-energize. This removes supply voltage to the primary ECM and the secondary ECM. The primary ECM and the secondary ECM will power down. The injection signals to the injector solenoids will stop. The air shutoff timer will allow the air shutoff relay to deactivate after 2.5 seconds. This prevents damage to the air shutoff solenoids.

The second condition occurs for an engine overspeed. The engine overspeed could be an actual overspeed condition or a simulated overspeed condition. The simulated overspeed condition can be obtained by using the Overspeed Verify Switch. The circuit will operate in the same manner that was described above.

The air shutoff relays can also be activated without the aid of the ECM. When the emergency stop switch on the instrument panel is depressed, the air shutoff relays are activated. Power from the "manual crank emergency stop breaker" energizes the air shutoff relays. The air shutoff timer will allow the air shutoff relay to deactivate after 2.5 seconds. This prevents damage to the air shutoff solenoids. The primary ECM and the secondary ECM will power down in the same manner that was explained above.

Regardless of the reason for activation, the Engine Control Switch (ECS) must be turned to the OFF/RESET position for three seconds. This resets the ECM and the air shutoff timer. In addition to turning the ECS to the OFF/RESET position, the operator must manually open the air shutoff valves before starting the engine.

Illustration 1	g00973881
Typical example

Test Step 1. Check for Connector Damage.

1. Verify that the circuit breakers are not tripped.

2. Turn the circuit breaker for the battery to the OFF position.

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

4. 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.

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

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

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

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

Expected Result:

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

Results:

• OK - The connectors and wiring are okay. Proceed to Test Step 2.

• Not OK - The connectors and/or wiring are not okay.

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

  STOP

Test Step 2. Test the Air Shutoff System.

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

2. Turn the ECS to the STOP position. The engine should be off.

3. Activate the overspeed verify switch.

4. Monitor the air shutoff solenoids.

Expected Result:

The air shutoff relays should activate.

Results:

• OK - The air shutoff solenoids activated 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 air shutoff solenoids failed to activate. Proceed to Test Step 3.

Test Step 3. Test for Voltage from the Air Shutoff Relay to the Air Shutoff Solenoids.

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

2. The output to the solenoids is terminal 30 on the air shutoff relays. The wires to the solenoids are 395-BR(Brown) and 394-BR(Brown). Connect a voltmeter between terminal 30 on the air shutoff relay and the engine ground.

3. Turn the ECS to the STOP position. The engine should be off.

4. Activate the overspeed verify switch.

5. Monitor the voltage on the voltmeter.

6. If a second air shutoff relay is installed, repeat the above steps for the other air shutoff relay.

Expected Result:

The voltage should measure 24 ± 3 VDC for 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for 2.5 seconds. The relay is operating correctly. Proceed to Test Step 4.

• Not OK - The voltage did not measure 24 ± 3 VDC for 2.5 seconds. Proceed to Test Step 5.

Test Step 4. Test for Voltage at the Air Shutoff Solenoids.

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

2. At the solenoid, disconnect the wires that go to the air shutoff solenoid.

3. Use a voltmeter to monitor the voltage at the air shutoff solenoid. Connect the voltmeter between the wires that were removed from the solenoid in the previous step.

4. Turn the ECS to the STOP position. The engine should be off.

5. Activate the overspeed verify switch.

6. Monitor the voltage on the voltmeter.

7. If a second air shutoff solenoid is installed, repeat the above steps for the other air shutoff solenoid.

Expected Result:

The voltage should measure 24 ± 3 VDC for 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for 2.5 seconds. The circuit is operating correctly to this point.

  Repair: Temporarily install a new air shutoff solenoid. Ensure that the problem is no longer present. Reinstall the old solenoid. If the problem returns, replace the air shutoff solenoid.

  STOP

• Not OK - The voltage did not measure 24 ± 3 VDC for 2.5 seconds. System voltage was not available at the solenoid. There is a problem in the wiring between the air shutoff solenoids and the air shutoff relays.

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

  STOP

Test Step 5. Check the Voltage at the Coil of the Air Shutoff Relays.

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

2. Connect a voltmeter between F708-YL(Yellow) on the air shutoff relay and the engine ground.

3. Turn the ECS to the STOP position. The engine should be off.

4. Activate the overspeed verify switch.

5. Monitor the voltage on the voltmeter.

6. If a second air shutoff solenoid is installed, repeat the above steps for the other air shutoff solenoid.

Expected Result:

The voltage should measure 24 ± 3 VDC for 2.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for 2.5 seconds. Proceed to Test Step 6.

• Not OK - The voltage did not measure 24 ± 3 VDC for 2.5 seconds. Proceed to Test Step 7.

Test Step 6. Check the Resistance at the Connector of the Air Shutoff Timer.

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

2. Disconnect the connector to the air shutoff timer.

3. Check the resistance at the connector of the air shutoff timer. Check the resistance between wire 200-BK(Black) on P-1 and the engine ground.

4. Check the resistance at the connector of the air shutoff timer. Check the resistance between wire F708-YL(Yellow) on P-2 and wire 055-WH(White) on P-3.

Expected Result:

The resistance of the wire on P-1 should be less than 5 Ohms. The resistance between the wires on P-2 and P-3 should be approximately 260 Ohms if one relay is present. The resistance between the wires on Pin 2 and Pin 3 should be approximately 130 Ohms when two relays are present.

Results:

• OK - The resistance on the wires meets the above requirements. The relay coils are okay. The relay's NORMALLY OPEN contacts may be faulty.

  Repair: Remove the wires from the NORMALLY OPEN contacts on the air shutoff relay. Check the resistance across the contacts as the air shutoff relay is energized. If the resistance is less 5 Ohms, the relay is okay. If the resistance is more than 5 Ohms, replace the relay. Ensure that the problem is no longer present. If the air shutoff relay is okay, replace the air shutoff timer. Verify that this solves the problem.

  STOP

• Not OK - The resistance does not meet the above requirements. Check the coil of the air shutoff relay for an open. The coil resistance should be approximately 260 Ohms.

  Repair: Replace the air shutoff relay if the coil of the relay is bad. Repair the connectors or wiring and/or replace the connectors or wiring.

  STOP

Test Step 7. Check the Voltage to the Overspeed Verify Switch.

1. For the following test step, disconnect wire 200-BK(Black) from terminal 85 of the emergency stop relay. Reconnect wire 200-BK(Black) to terminal 85 of the emergency stop relay after completing this test step.

2. Turn the ECS to the STOP position. The engine should be off.

3. Verify that 24 ± 3 VDC is present on terminal 5 of the ECS. If voltage is not present on terminal 5 of the ECS, perform the diagnostic functional test Troubleshooting, "Engine Control Switch (ECS)".

4. Verify that 24 ± 3 VDC is present on terminal 1 of the emergency stop switch. If voltage is not present on terminal 1 of the emergency stop switch, perform the diagnostic functional test Troubleshooting, "Emergency Stop Switch".

5. Measure the voltage on terminal 2 of the overspeed verify switch.

Expected Result:

The voltage should measure 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC. Proceed to Test Step 8.

• Not OK - The voltage does not measure 24 ± 3 VDC. Proceed to Test Step 9.

Test Step 8. Check the Input Voltage to the Primary ECM from the Overspeed Verify Switch.

1. For the following test step, disconnect wire 200-BK(Black) from terminal 85 of the emergency stop relay. Reconnect wire 200-BK(Black) to terminal 85 of the emergency stop relay after completing this test step.

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

3. Disconnect the primary ECM connector P1.

4. Connect a voltmeter between the primary ECM connector P1-27 and the engine ground.

5. Turn the ECS to the STOP position. The engine should be off.

6. Activate the overspeed verify switch.

7. Monitor the voltage on the voltmeter.

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

9. Reconnect the primary ECM connector P1.

Expected Result:

The voltage should measure 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC. Proceed to Test Step 10.

• Not OK - The voltage does not measure 24 ± 3 VDC.

  Repair: Verify that 24 ± 3 VDC is present on terminal 3 of the overspeed verify switch when the switch is activated. If voltage is present on terminal 3 of the overspeed verify switch, repair the wire F706-PU(Purple) between the primary ECM and the overspeed verify switch.

  If 24 ± 3 VDC is not present on terminal 3 of the overspeed verify switch, replace the overspeed verify switch.

  STOP

Test Step 9. Check the Voltage at the Coil of the Primary ECM Relay.

1. For the following test step, disconnect wire 200-BK(Black) from terminal 85 of the emergency stop relay. Reconnect wire 200-BK(Black) to terminal 85 of the emergency stop relay after completing this test step.

2. Turn the ECS to the STOP position. The engine should be off.

3. Measure the voltage between terminal 86 of the primary ECM relay and the engine ground.

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

Expected Result:

The voltage should measure 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC.

  Repair: Check for 24 ± 3 VDC on terminal 87 and on terminal 30 of the primary ECM relay. If voltage is present on both terminals, repair the wire 150-OR(Orange) between the primary ECM relay and the overspeed verify switch.

  If voltage is not present on terminal 30 of the primary ECM relay, check the wire 200-BK(Black) on terminal 85 of the primary ECM relay for continuity to engine ground. If the wire is okay, replace the primary ECM relay. Verify that the circuit is working correctly.

  If voltage is not present on terminal 87 of the primary ECM relay, ensure that the circuit breakers are not tripped. Check the wiring between the "ECM breaker" and the primary ECM relay.

  STOP

• Not OK - The voltage does not measure 24 ± 3 VDC.

  Repair: Disconnect the wire 103-RD(Red) from terminal 86 of the primary ECM relay. Check the wire 103-RD(Red) for continuity to terminal 1 of the emergency stop switch. Verify that the normally closed contacts on the "emergency stop lockout relay" are operating properly. If necessary, repair the wire or replace the relay .

  STOP

Test Step 10. Check the Output Voltage from the Air Shutoff at the Secondary ECM.

1. For the following test step, disconnect wire 200-BK(Black) from terminal 85 of the emergency stop relay. Reconnect wire 200-BK(Black) to terminal 85 of the emergency stop relay after completing this test step.

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

3. Disconnect P1 from the Secondary ECM. Remove the wire F708-YL(Yellow) from P1-28.

4. Install a jumper wire in P1-28. Reconnect the Secondary ECM connector P1.

5. Connect the voltmeter between the jumper wire that is in P1-28 and the engine ground.

6. Turn the ECS to the STOP position. The engine should be off.

7. Activate the overspeed verify switch.

8. Monitor the voltage on the voltmeter.

9. Turn the ECS to the OFF/RESET position. Remove the jumper wire and replace wire F708-YL(Yellow). Reconnect ECM connector P1.

Expected Result:

The voltage should measure 24 ± 3 VDC for 1.5 seconds.

Results:

• OK - The voltage measures 24 ± 3 VDC for 1.5 seconds. The voltage was present at the ECM connector. Proceed to Test Step 11.

• Not OK - The voltage did not measure 24 ± 3 VDC for 1.5 seconds.

  Repair: The primary ECM sends a signal over the CAT Data Link to the secondary ECM in order to activate the output for the air shutoff. Verify that the CAT Data Link is operating correctly. Refer to the diagnostic functional test Troubleshooting, "CAT Data Link" for reference.

  If the CAT Data Link is operating correctly, check for active diagnostic codes for the primary ECM or for the secondary ECM.

  STOP

Test Step 11. Check the Voltage at the Emergency Stop Switch.

1. For the following test step, disconnect wire 200-BK(Black) from terminal 85 of the emergency stop relay. Reconnect wire 200-BK(Black) to terminal 85 of the emergency stop relay after completing this test step.

2. Turn the ECS to the STOP position. The engine should be off.

3. Connect a voltmeter between terminal 7 on the emergency stop switch and engine ground.

4. Activate the overspeed verify switch.

5. Monitor the voltage on the voltmeter.

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

Expected Result:

The voltage should measure 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC. Proceed to Test Step 12.

• Not OK - The voltage does not measure 24 ± 3 VDC.

  Repair: Repair the wire F708-YL(Yellow) between the emergency stop switch and the secondary ECM.

  STOP

Test Step 12. Check the Voltage at the Coil of the "Emergency Stop Lockout Relay".

1. For the following test step, disconnect wire 200-BK(Black) from terminal 85 of the emergency stop relay. Reconnect wire 200-BK(Black) to terminal 85 of the emergency stop relay after completing this test step.

2. Turn the ECS to the STOP position. The engine should be off.

3. Connect a voltmeter between terminal 86 on the "emergency stop lockout relay" and engine ground.

4. Activate the overspeed verify switch.

5. Monitor the voltage on the voltmeter.

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

Expected Result:

The voltage should measure 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC. Proceed to Test Step 13.

• Not OK - The voltage does not measure 24 ± 3 VDC.

  Repair: Repair the wire 103-RD(Red) between the "emergency stop lockout realy" and terminal 7 on the emergency stop switch.

  STOP

Test Step 13. Check the Voltage on Terminal 30 of the "Emergency Stop Lockout Relay".

1. For the following test step, reconnect wire 200-BK(Black) to terminal 85 of the emergency stop relay.

2. Turn the ECS to the STOP position. The engine should be off.

3. Connect a voltmeter between terminal 30 on the "emergency stop lockout relay" and engine ground.

4. Activate the overspeed verify switch.

5. Monitor the voltage on the voltmeter.

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

Expected Result:

The voltage should measure 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC. Proceed to Test Step 14.

• Not OK - The voltage does not measure 24 ± 3 VDC.

  Repair: Check for 24 ± 3 VDC on terminal 87 of the "emergency stop lockout relay". If voltage is present on terminal 87 of the "emergency stop lockout relay", check the wire 200-BK(Black) on terminal 85 of the "emergency stop lockout relay" for continuity to engine ground. If the wire is okay, replace the "emergency stop lockout relay". Verify that the circuit is working correctly.

  If voltage is not present on terminal 87 of the "emergency stop lockout relay", check the wire 103-RD(Red) between terminal 87 of the "emergency stop lockout relay" and the ECS. If necessary, repair the wire.

  STOP

Test Step 14. Check the Voltage at the Coil of the Emergency Stop Relay.

1. For the following test step, reconnect wire 200-BK(Black) to terminal 85 of the emergency stop relay.

2. Turn the ECS to the STOP position. The engine should be off.

3. Connect a voltmeter between terminal 86 on the emergency stop relay and engine ground.

4. Activate the overspeed verify switch.

5. Monitor the voltage on the voltmeter.

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

Expected Result:

The voltage should measure 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC. Proceed to Test Step 15.

• Not OK - The voltage does not measure 24 ± 3 VDC.

  Repair: Repair the wire 103-RD(Red) between the "emergency stop lockout relay" and terminal 86 on the emergency stop relay.

  STOP

Test Step 15. Check the Voltage on Terminal 87 of the Emergency Stop Relay.

1. For the following test step, reconnect wire 200-BK(Black) to terminal 85 of the emergency stop relay.

2. Turn the ECS to the STOP position. The engine should be off.

3. Connect a voltmeter between terminal 87 on the emergency stop relay and engine ground.

4. Activate the overspeed verify switch.

5. Monitor the voltage on the voltmeter.

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

Expected Result:

The voltage should measure 24 ± 3 VDC.

Results:

• OK - The voltage measures 24 ± 3 VDC.

  Repair: Repair the wire F708-YL(Yellow) between terminal 87 of the emergency stop relay and terminal 86 of the air shutoff relays.

  STOP

• Not OK - The voltage does not measure 24 ± 3 VDC.

  Repair: Check for 24 ± 3 VDC on terminal 30 of the emergency stop relay. If voltage is present on terminal 87 of the emergency stop relay, check the wire 200-BK(Black) on terminal 85 of the emergency stop relay for continuity to engine ground. If the wire is okay, replace the emergency stop relay. Verify that the circuit is working correctly.

  If voltage is not present on terminal 30 of the emergency stop relay, check the wire 103-RD(Red) between terminal 30 of the emergency stop relay and terminal 7 on the emergency stop switch. If necessary, repair the wire.

  STOP