System Operation Description:
The Air Inlet Shutoff is available for certain engine ratings that operate in areas with large amounts of combustible gases. The air inlet shutoff will protect the engine from an overspeed when these gases are present. When an overspeed is detected, a relay activates the air inlet shutoff and injection is disabled until the engine speed reaches 0 rpm. This is accomplished by closing a flap in order to cut off the air supply to the engine. Once the Air Inlet Shutoff is activated the flap must be manually reset before the engine can be restarted.
Test Step 1. Perform the “Air Inlet Shutoff System Control Test”
A. Turn the keyswitch to the OFF position.
B. Connect the Caterpillar Electronic Technician (Cat ET) to the data link connector.
C. Turn the keyswitch to the ON position.
D. Start the engine. Increase the engine speed from low idle to 1400 rpm to 1600 rpm.
E. Go to the “Air Inlet Shutoff System Control Test” on Cat ET.
F. Start 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. The air
inlet shutoff is working correctly.
Repair: Reset the air inlet shutoff system. Talk to the operator in order to determine the reason for the overspeed.
STOP.
• Not OK – The engine did not shut down. Proceed to Test Step 2.
Test Step 2. Check the Interlock for the
Air Inlet Shutoff
A. Verify that J1/P1:62 (Output 12) is connected to the +Battery.
Expected Result:
J1/P1:62 is connected to the +Battery.
Results:
• OK – J1/P1:62 (Output 12) is connected to the +Battery. Proceed to Test Step 3.
• Not OK – J1/P1:62 (Output 12) is not connected to the +Battery.
Repair: Connect J1/P1:62 to the +Battery. Repeat Test Step 1.
Test Step 3. Inspect Electrical Connectors and Wiring
A. Turn the keyswitch to the OFF/RESET position.
B. Thoroughly inspect the J2/P2 ECM connector and all other connectors in the circuit. Refer to Troubleshooting, “Electrical Connectors – Inspect” for details.
C. Perform a 45 N (10 lb) pull test on the wires that are associated with the air inlet shutoff system.
D. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).
E. Check the harness and wiring for abrasion and for pinch points from the sensors back to the ECM.
Expected Result:
All connectors, pins and sockets should be completely coupled and/or inserted and the harness and wiring should be free of corrosion, abrasion or pinch points.
Results:
• OK – All the wires and connections are OK. Proceed to Test Step 4.
• 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 4. Perform the “Air Inlet Shutoff Relay Output” Test
A. Turn the keyswitch to the OFF position.
B. Connect Cat ET to the data link connector.
C. Turn the keyswitch to the ON position. Do not start the engine.
D. Go to the “Air Inlet Shutoff Relay Output” test on Cat ET.
E. Start the test and listen for a click from the relay for the air inlet shutoff.
Expected Result:
The relay is active.
Results:
• OK – A click is heard. The relay is active. Proceed to Test Step 5.
• Not OK – There is a problem with the relay circuit.
Proceed to Test Step 7.
Test Step 5. Check the Supply Voltage to the Air Inlet Shutoff Solenoid
A. Turn the keyswitch to the ON position.
B. Proceed to the “Air Inlet Shutoff Relay Output” test on Cat ET.
C. Activate the relay for the air inlet shutoff solenoid.
D. Use a voltage test lamp to check the voltage across the two terminals of the air inlet shutoff solenoid.
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 ECM is properly controlling the relay for the air inlet shutoff solenoid, but the air inlet shutoff solenoid is not working. Proceed to Test Step 6.
• Not OK – The air inlet shutoff solenoid is not receiving the correct signal. Proceed to Test Step 10.
Test Step 6. Check the Resistance of the Solenoid
A. Disconnect the wires for the air inlet shutoff solenoid.
B. Measure the resistance of the air inlet shutoff solenoid.
C. Reconnect the wires for the air inlet shutoff solenoid.
Expected Result:
Resistance should be 15 to 20 Ohms.
Results:
• OK – The resistance of the air inlet shutoff solenoid is OK.
Repair: Check electrical connections. Refer to Troubleshooting, “Electrical Connectors – Inspect”
for more information.
STOP.
• Not OK – The resistance of the solenoid is out of specification.
Repair: Replace the air inlet shutoff solenoid.
Verify that the repair eliminates the problem.
STOP.
Test Step 8. Check the Signal Voltage to the Relay
A. Unplug the relay for the air inlet shutoff solenoid from the ECM.
B. Turn the key switch to the ON position.
C. Proceed to the “Air Inlet Shutoff Relay Output” test on Cat ET.
D. Activate the system for the air inlet shutoff solenoid.
Note: The output for the air inlet shutoff system will be active for only one second.
E. Check the voltage between P520:1 (Solenoid Common) and P520:2 (Air Inlet Shutoff Output)
with a voltage test lamp.
Expected Result:
The voltage test lamp illuminates when the test is active.
Results:
• OK – The relay is receiving the signal from the ECM. Proceed to Test Step 9.
• Not OK – The relay is not receiving the signal from the ECM. Proceed to Test Step 11.
Test Step 9. Check the Power Supply to the Relay
A. Measure the voltage between the +Battery terminal of the relay and the engine ground.
Expected Result:
The voltage should be 12.0 ± 4.0 VDC.
Results:
• OK – The relay is receiving power. Proceed to Test Step 10.
• Not OK – There is a problem in the wiring between the relay and the +Battery terminal.
Repair: Repair the circuit.
Verify that the repair eliminates the problem.
STOP.
Test Step 10. Check the Output Voltage of the Relay
A. Ensure that all connectors are connected to the wiring harness.
B. Turn the key switch to the ON position.
C. Go to the “Air Inlet Shutoff Relay Output” test on Cat ET.
D. Activate the system for the air inlet shutoff solenoid.
Note: The output for the air inlet shutoff system will be active for only one second.
E. Check the voltage from the output terminal on the relay to the engine ground with a voltage test lamp.
Expected Result:
The voltage test lamp illuminates when the test is active.
Results:
• OK – There is a problem in the wiring between the relay and the air inlet shutoff solenoid.
Repair: Repair the circuit.
Verify that the repair eliminates the problem.
STOP.
• Not OK – The relay is not sending power to the air inlet shutoff solenoid. The relay is bad.
Repair: Replace the relay for the air inlet shutoff.
Verify that the repair eliminates the problem.
STOP.
Test Step 11. Check for Shorts in the Wiring Harness between the Relay and the ECM
A. Ensure that the keyswitch is in the OFF/RESET position.
B. Disconnect the J2/P2 ECM connector.
C. Unplug the relay for the air inlet shutoff.
D. Measure the resistance between P2:13 (Air Inlet Shutoff Output) and P2:9 (Solenoid Common).
Expected Result:
The resistance should be greater than 20,000 Ohms.
Results:
• OK – There are no shorts in the wiring harness.
Proceed to Test Step 12.
• Not OK – There is a short in the wiring harness between the ECM and the relay.
Repair: Repair the circuit.
Verify that the repair eliminates the problem.
STOP.
Test Step 12. Check the Relay Signal at the ECM
A. Turn the keyswitch to the OFF/RESET position.
B. Remove the wire from P2:13 (Air Inlet Shutoff Output) in the P2 ECM connector.
C. Turn the keyswitch to the ON position.
D. Activate the “Air Inlet Shutoff Relay Output” test on Cat ET.
Note: The output for the air inlet shutoff system will be active for only one second.
E. Check the voltage between the open terminal at P2:13 (Air Inlet Shutoff Output) and P2:9 (Solenoid Common) with a voltage test lamp.
F. Turn the keyswitch to the OFF/RESET position.
G. Reinstall the wire to P2:13 (Air Inlet Shutoff Output).
Expected Result:
The voltage test lamp illuminates when the test is active.
Results:
• OK – The ECM is supplying the correct voltage.
There is an open circuit in the harness.
Repair: Repair the circuit.
Verify that the repair eliminates the problem.
STOP.
• Not OK – The ECM is not supplying the correct voltage.
Repair: Verify your results. Replace the ECM.
Refer to Troubleshooting, “Replacing the ECM” before replacing the ECM.
Verify that the repair eliminates the problem.
STOP.
