3406E and 3456 Generator Set Engines Caterpillar

The Electronic Control Module (ECM) has the ability to stop the engine by shutting off the inlet air supply in an emergency situation. The ECM activates a relay which energizes the air shutoff solenoid. The solenoid actuates the air shutoff valve.

There are two conditions which can cause the ECM to activate the air shutoff relay. The first condition occurs when the operator activates the remote emergency stop button. When the emergency shutdown is recognized, the ECM will stop the injection of fuel and the air shutoff relay is activated. The ECM will hold the relay active for 1.5 seconds. The second condition occurs when the ECM detects an engine overspeed. This is simulated when the overspeed verify switch is activated. When the engine speed reaches 75 percent of the programmed overspeed setpoint, the ECM will activate the air shutoff relay. The second condition can also occur when a test of the air shutoff relay is made. Again, this is used for testing purposes.

Regardless of the reason for the activation, the engine control switch (ECS) must be turned to the OFF/RESET position for at least three seconds. Turning the ECS to the OFF/RESET position will reset the engine control. Also, turning the ECS to the OFF/RESET position will reset the relay that operates the air shutoff relay.

Illustration 1	g01067849
Schematic for the air shutoff system

Test Step 1. CHECK THE ELECTRICAL CONNECTORS AND THE WIRING

1. Verify that the air shutoff valves are set to the OPEN position.

2. Thoroughly inspect the ECM connector J1/P1, and the customer connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

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

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

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

6. Check the harness and the wiring for abrasion and for pinch points from the air shutoff solenoid to the ECM. Refer to Illustration 1.

Expected Result:

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

Results:

• OK - Proceed to Test Step 2.

• Not OK - Repair the wiring and connectors or replace the wiring or the connectors. Ensure that all of the seals are properly connected. Verify that the repair eliminates the problem.

  STOP

Test Step 2. TEST THE OUTPUT OF THE AIR SHUTOFF RELAY

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

2. Turn the ECS to the STOP position.

3. Connect the Caterpillar Electronic Technician (ET) to the service tool connector.

4. Access the "Override Parameters" screen on Cat ET.

5. Disable the "Air Shutoff Override".

Expected Result:

The air shutoff relay activates.

Results:

• OK - The relay and the solenoid for the air shutoff system are operating properly at this time. There may be an intermittent electrical problem in the air shutoff circuit.

  Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The relay activated but the air shutoff solenoid did not activate. Proceed to Test Step 3.

Test Step 3. TEST THE ECM OUTPUT

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

2. Disconnect P1 ECM connector from the ECM. Remove P1:34 air shutoff relay.

3. Fabricate a jumper wire 100 mm (4 inch) long. Crimp a Deutsch Pin to both ends of the wire.

4. Connect a test lamp at the air shutoff solenoid between the wire from the normally open contact of the air shutoff relay and engine ground.

5. Insert one end of the jumper wire into P1:34 air shutoff relay and reconnect P1 ECM connector.

6. Connect one probe of the voltage test lamp to -Battery and the other probe to the socket of the jumper wire at P1:34 air shutoff relay.

7. Turn the circuit breaker for the battery circuit to the ON position. Turn the ECS to the STOP position.

8. Access the "Override Parameters" screen on Cat ET and activate the "Air Shutoff Override".

   Note: This test will cause 446-05 Air Shutoff Relay open to be logged. Clear this diagnostic code after completion of this test procedure.

9. Disable the air shutoff relay. Turn the ECS to the OFF/RESET position and remove the jumper wire.

Expected Result:

The test lamp illuminates for at least 1.5 seconds.

Results:

• OK - The test lamp illuminated.

  Repair: The problem is not with the ECM.

  Proceed to Test Step 4.

• Not OK - The test lamp did not illuminate.

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

  STOP

Test Step 4. TEST THE AIR SHUTOFF RELAY

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

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

3. Disconnect P1:34 from the air shutoff relay.

4. Fabricate a jumper wire 100 mm (4 inch) long. Crimp a Deutsch Pin to both ends of the wire.

5. Disconnect the wire from terminal 86 of the air shutoff relay.

6. Connect one end of the jumper wire to the +Battery and the other end of the jumper wire to the terminal 86 of the air shutoff relay for two seconds.

7. Remove the jumper wire and reconnect all of the terminal connections.

Expected Result:

The air shutoff solenoid activates. The air shutoff solenoid clicks ON when the jumper wire is connected to the +Battery.

Results:

• OK - The air shutoff relay is operating properly.

  Repair: The problem is most likely in the wiring between the one-shot relay and the air shutoff relay. Repair the wiring. Verify that the repair has eliminated the problem.

  STOP

• Not OK - The air shutoff solenoid did not activate.

  Repair: The air shutoff relay is suspect. Temporarily install a new air shutoff relay. If the problem is solved with the new air shutoff relay, reinstall the suspect air shutoff relay. If the problem returns, replace the air shutoff relay.

  Proceed to Test Step 5.

Test Step 5. CHECK THE AIR SHUTOFF SOLENOID

1. Turn the ECS to the OFF position.

2. Disconnect the wires from the positive terminal and negative terminals of the air shutoff solenoid.

3. Fabricate two jumper wires 100 mm (4 inch) long.

4. Connect one end of the first jumper wire to the negative terminal of the air shutoff solenoid and connect the other end of the jumper wire to the -Battery terminal.

5. Connect one end of the second jumper wire to the +Battery terminal and the other end of the jumper wire to the positive terminal of the air shutoff solenoid.

Expected Result:

The air shutoff solenoid clicks ON when the second jumper wire is connected to the positive terminal of the air shutoff solenoid and to the +Battery terminal.

Results:

• OK - The air shutoff solenoid activated.

  Repair: The problem appears to be in the wiring. Perform the following repair. Repair the wiring and/or replace the wiring. Verify that the repair eliminated the problem.

  1. Check the wiring between the -Battery and the negative terminal of the air shutoff solenoid.

  2. Check the wiring between the positive terminal of the air shutoff solenoid and terminal 87 of the air shutoff relay.

  3. Check the wiring between the P1:34 air shutoff relay and the +Battery terminal.

  STOP

• Not OK - The air shutoff solenoid did not activate.

  Repair: The problem appears to be in the air shutoff solenoid. Temporarily install a new air shutoff solenoid. If the problem is resolved, reinstall the suspect solenoid. If the problem returns with the suspect air shutoff solenoid, replace the air shutoff solenoid.

  STOP