C13 and C15 Engines for Combat and Tactical Vehicles Caterpillar

The air inlet shutoff is available for certain engine ratings that operate in areas with large amounts of combustible gases. When an overspeed is detected, a relay activates the air inlet shutoff system and fuel injection is disabled. This is accomplished by activation of a solenoid that closes a flap that is in the inlet air system in order to cut off the air supply to the engine. Once the air inlet shutoff is activated the flap must be manually reset to the open position, before the engine can be restarted.

"Air Inlet Shutoff System Control Test"

Caterpillar Electronic Technician (ET) allows the use of the "Air Inlet Shutoff System Control Test" in order to test the air inlet shutoff system. This test will determine if the air inlet shutoff system is working correctly. When the test is activated the air inlet shutoff will activate and the engine will shut down. The engine speed must be 1500 rpm ± 100 rpm and the transmission must be in neutral before this test can be used.

"Air Inlet Shutoff Relay Output"

The "Air Inlet Shutoff Relay Output" test is available to energize the air inlet shutoff relay. When the test is activated, a one second pulse is sent to the air inlet shutoff relay. The engine speed must be 0 rpm and the transmission must be in neutral before this test can be used.

Air Inlet Shutoff Switch

The air inlet shutoff switch can be used to manually activate the air inlet shutoff. When the switch is depressed, a one second pulse is sent to the air inlet shutoff relay. The transmission must be in neutral before the air inlet shutoff switch will become active.

Illustration 1	g01453543
Schematic for the air inlet shutoff circuit

Test Step 1. Perform the "Air Inlet Shutoff System Control Test"

1. Turn the keyswitch to the OFF position.

2. Connect Cat ET to the service tool connector.

3. Turn the keyswitch to the ON position.

4. Place the transmission in the neutral position.

5. Start the engine. Increase the engine speed from low idle to 1500 rpm ± 100 rpm.

6. Access the "Air Inlet Shutoff System Control Test" in the "Diagnostic Tests" under the "Diagnostics" menu on Cat ET.

7. Start the test.

8. Wait for the engine to stop.

9. Stop the test.

Expected Result:

Fuel injection is disabled. The air inlet shutoff is activated and the engine is shutdown.

Results:

• OK - The engine is shutdown when the "Air Inlet Shutoff System Control Test" is activated.

  Repair: The air inlet shutoff is working correctly. Reset the air inlet shutoff system.

  Proceed to Test Step 2.

• Not OK - The engine did not shut down. Proceed to Test Step 4.

Test Step 2. Check the Air Inlet Shutoff Switch

1. Turn the keyswitch to the ON position.

2. Use Cat ET to monitor the status for the air inlet shutoff switch while the switch is depressed.

Expected Result:

The switch status reports "On" when the switch is depressed. The status reports "Off" when the switch is released.

Results:

• OK - The switch status reports "On" when the switch is depressed. The status reports "Off" when the switch is released.

  Repair: The switch is operating correctly. The air inlet shutoff system appears to be operating correctly at this time. There may be an intermittent problem in the harness or in a connector. If an intermittent problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for details that are related to troubleshooting intermittent electrical problems.

  STOP

• Not OK - One of the following conditions exist: The switch status does not report "On" when the switch is depressed. The switch status does not report "Off" when the switch is released. The switch is not operating correctly. There is a problem in the switch circuit. Proceed to Test Step 3.

Test Step 3. Check the Circuit for the Air Inlet Shutoff Switch

1. Turn the keyswitch to the OFF position.

2. Disconnect the air inlet shutoff switch at the harness connector.

3. Turn the keyswitch to the ON position.

4. Short circuit the wires that are for the air inlet shutoff switch. Monitor the status for the air inlet shutoff switch while the two wires from the switch are connected.

Expected Result:

The status is "On" when the wires are connected. The status is "Off" when the wires are disconnected.

Results:

• OK - The status is "On" when the wires are connected. The status is "Off" when the wires are disconnected.

  Repair: There is a problem with the switch. Replace the air inlet shutoff switch.

  Verify that the repair eliminates the problem.

  STOP

• Not OK - One of the following conditions exist: The switch status is not "On" when the wires are shorted. The switch status is not "Off" when the wires are disconnected.

  Repair: There is a problem between the Engine Control Module (ECM) and the air inlet shutoff switch. Inspect the wiring between the ECM and the air inlet shutoff switch.

  Repair the wiring or replace the wiring.

  Verify that the repair eliminates the original problem.

  STOP

Test Step 4. Check the Interlock for the Air Inlet Shutoff

1. If a transmission neutral switch is installed, verify that the transmission is in neutral. Verify that the transmission neutral switch is connected to J1-62. Also, verify that battery power is available on J1-62.

2. If a transmission neutral switch is not installed, verify that J1-62 is wired to battery power.

Expected Result:

The transmission is in neutral and/or J1-62 is connected to battery power.

Results:

• OK - Battery power is present on terminal J1-62 at the ECM.

  Repair: Check the status for the "Transmission Neutral Switch" while the transmission is in neutral.

  The status should be "On".

  If the status is "Off", troubleshoot the circuit for the neutral switch. Refer to Troubleshooting, "Neutral Switch Circuit - Test" for details. Make the necessary repairs.

  Proceed to Test Step 5.

• Not OK - Battery power is not present on terminal J1-62 at the ECM.

  Repair: Troubleshoot the circuit for the transmission neutral switch or connect J1-62 to battery power.

  Repeat Test Step 1.

Test Step 5. Inspect the Electrical Connectors and the Wiring

1. Turn the keyswitch to the OFF position.
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   Illustration 2	g01453550
   Location of the ECM connectors for the air inlet shutoff system (1) J2/P2 ECM connectors (2) J1/P1 ECM connectors

2. Thoroughly inspect ECM connector (1) and (2). Also, thoroughly inspect all of the other connectors in the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
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   Illustration 3	g01327392
   Terminal locations at the P1 ECM connector for the air inlet shutoff system (P1-3) Return (P1-46) Air inlet shutoff switch

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   Illustration 4	g01453545
   Terminal locations at the P2 ECM connector for the air inlet shutoff system (P2-6) Air inlet shutoff relay (P2-14) Return

3. Perform a 45 N (10 lb) pull test on the wires that are associated with the air inlet shutoff system.

4. Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

5. Check the harness and wiring for abrasion and for pinch points from each of the circuit components back to the ECM.

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 - All the wires and connections are OK. Proceed to Test Step 6.

• Not OK -

  Repair: Perform the following 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 6. Perform the "Air Inlet Shutoff Relay Output" Test

1. Turn the keyswitch to the ON position. Do not start the engine.

2. Go to the "Air Inlet Shutoff Relay Output" test on Cat ET.

3. Activate the "Air Inlet Shutoff Relay Output" test on Cat ET and listen for an audible click from the air inlet shutoff relay.

Expected Result:

An audible click is heard from the air inlet shutoff relay.

Results:

• OK - An audible click is heard. The relay energizes. Proceed to Test Step 7.

• Not OK - An audible click is not heard. The relay does not energize. There is a problem with the relay circuit. Proceed to Test Step 9.

Test Step 7. Check the Supply Voltage to the Air Inlet Shutoff Solenoid

1. Turn the keyswitch to the OFF position.

2. Disconnect the wires from the air inlet shutoff solenoid.

3. Connect a voltage test lamp between the wires that were disconnected from the air inlet shutoff solenoid.

4. Turn the keyswitch to the ON position.

5. Activate the "Air Inlet Shutoff Relay Output" test on Cat ET.

   Note: The output for the air inlet shutoff will be active for only one second.

Expected Result:

The voltage test lamp illuminates when the test is active.

Results:

• OK - The voltage test lamp illuminates. Voltage is present at the air inlet shutoff solenoid but the air inlet shutoff solenoid is not working.

  Repair: Replace the air inlet shutoff solenoid. Verify that the repair eliminates the problem.

  STOP

• Not OK - The voltage test lamp does not illuminate. Voltage is not present at the air inlet shutoff solenoid. Verify that there is continuity on the wire between the air inlet shutoff solenoid and engine ground. If necessary, repair the wire. If the wire is OK, proceed to Test Step 8.

Test Step 8. Check the Output Voltage from the Normally Open Contacts of the Air Inlet Shutoff Relay

1. Ensure that all connectors are connected to the wiring harness.

2. Turn the keyswitch to the OFF position.

3. Disconnect the wire from the normally open contact of the air inlet shutoff relay that goes to the air inlet shutoff solenoid.

4. Connect a voltage test lamp between the normally open contact of the air inlet shutoff relay and engine ground.

5. Turn the keyswitch to the ON position.

6. Activate the "Air Inlet Shutoff Relay Output" test on Cat ET.

   Note: The output for the air inlet shutoff will be active for only one second.

Expected Result:

The voltage test lamp illuminates when the test is active.

Results:

• OK - The voltage test lamp illuminates when the test is active.

  Repair: There is a problem in the wiring between the air inlet shutoff relay and the air inlet shutoff solenoid. Repair the circuit.

  Verify that the repair eliminates the problem.

  STOP

• Not OK - The voltage test lamp does not illuminate when the test is active.

  Repair: Verify that battery voltage is present on the other side of the normally open contact of the air inlet shutoff relay. If voltage is not present to the relay, repair the wiring between the battery and the air inlet shutoff relay. If voltage is present at the relay, replace the air inlet shutoff relay. Verify that the repair eliminates the problem.

  STOP

Test Step 9. Check the Signal Voltage at the Connector for the Air Inlet Shutoff Relay

1. Turn the keyswitch to the OFF position.

2. Unplug the air inlet shutoff relay from the harness connector.

3. Connect a voltage test lamp between terminal 1 and terminal 2 on the connector for the air inlet shutoff relay.

4. Turn the keyswitch to the ON position.

5. Activate the "Air Inlet Shutoff Relay Output" test on Cat ET.

   Note: The output for the air inlet shutoff will be active for only one second.

Expected Result:

The voltage test lamp illuminates when the test is active.

Results:

• OK - The voltage test lamp illuminates.

  Repair: Voltage is present to the air inlet shutoff relay but the relay does not energize. Replace the air inlet shutoff relay. Verify that the repair eliminates the problem.

  STOP

• Not OK - The voltage test lamp does not illuminate. The relay is not receiving the signal from the ECM. Proceed to Test Step 10.

Test Step 10. Check for Proper Operation of the ECM

1. Ensure that the keyswitch is in the OFF position.

2. Disconnect the J2/P2 ECM connector.

3. Fabricate two jumper wires that are long enough to create a test circuit at the ECM connector. Crimp connector sockets to one end of each of the jumper wires.

4. Remove the wires from terminal locations P2-6 (air inlet shutoff) and P2-14 (return). Install the jumper wires into these terminal locations.

5. Connect a voltage test lamp between the jumper wires that were just installed.

6. Turn the keyswitch to the ON position.

7. Activate the "Air Inlet Shutoff Relay Output" test on Cat ET.

   Note: The output for the air inlet shutoff will be active for only one second.

Expected Result:

The voltage test lamp illuminates when the test is active.

Results:

• OK - The voltage test lamp illuminates when the test is active.

  Repair: The ECM is operating properly. The problem is in the wiring harness or in a connector between the ECM and the air inlet shutoff relay. Repair the wiring harness and/or the connector. Replace parts, if necessary.

  Verify that the repair eliminates the problem.

  STOP

• Not OK - The voltage test lamp does not illuminate when the test is active.

  Repair: There is a problem with the ECM. Perform the following procedure:

  1. Temporarily connect a test ECM.

     Refer to Troubleshooting, "Replacing the ECM".

  2. Recheck the circuit in order to ensure that the original problem has been resolved.

     If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved.

     If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring. Recheck the system.

  STOP