C18 Industrial Engine Caterpillar

Air Shutoff - Test

Usage:

C18 ZPS

Use this procedure to troubleshoot the following codes or if the air shutoff system is not operating properly.

Show/hide table

Table 1
Diagnostic Codes
CDL Code	J1939 Code	Code Description (code descriptions may vary)	Comments
3239-5	2813-5	Air Shutoff Relay : Current Below Normal	The code is logged.
3239-6	2813-6	Air Shutoff Relay : Current Above Normal	The code is logged.
Follow the troubleshooting procedure in order to identify the root cause of the problem.

Show/hide table




Illustration 1	g02176233
Typical schematic diagram

Note: The "Air Shutoff" parameter must be set to "Enabled" in order for the ECM to energize the air shutoff solenoid.

Show/hide table

Table 2
Troubleshooting Test Steps	Values	Results
1. Check for Diagnostic Trouble Codes A. Establish communication between Caterpillar Electronic Technician (ET) and the Electronic Control Module (ECM). Refer to Troubleshooting, "Electronic Service Tools", if necessary. B. Determine if a code is active or logged.	Diagnostic code	Result: A 3239-5, 3239-6, 2813-5 or a 2813-6 code is active or logged. Proceed to Test Step 11. Result: A 3239-5, 3239-6, 2813-5 or a 2813-6 code is not active or logged. Proceed to Test Step 2.
2. Perform the "Air Inlet Shutoff System Control Test" A. Turn the key switch to the OFF position. B. Connect Cat ET to the service tool connector. C. Turn the key switch to the ON position. D. Place the transmission in neutral. If the engine will not start, check the air inlet valve to ensure that the valve is not stuck closed. E. Start the engine. Increase the engine speed to 1500 rpm ± 100 rpm. F. Access the "Air Inlet Shutoff System Control Test" in the "Diagnostic Tests" under the "Diagnostics" menu on Cat ET. G. Start the test. H. Wait for the engine to stop. I. Stop the test.	Test was successful	Result: The engine is shut down when the "Air Inlet Shutoff System Control Test" is activated. The air inlet shutoff is working correctly. Reset the air inlet shutoff system. Proceed to Test Step 3. Result: The engine did not shut down. Proceed to Test Step 5.
3. Check the Air Inlet Shutoff Switch A. Turn the key switch to the ON position. B. Monitor the status for the air inlet shutoff switch while the switch is depressed.	Switch works correctly	Result: The switch is operating correctly. Return to service. Result: The switch is not operating correctly. Proceed to Test Step 4.
4. Check the Circuit to the Air Inlet Shutoff Switch A. Turn the key switch to the OFF position. B. Remove the air inlet shutoff switch. C. Turn the key switch to the ON position. D. Monitor the status for the air inlet shutoff switch while the two wires from the switch are connected.	The circuit is OK	Result: The indications are correct. The wiring is OK. The switch is not working properly. Replace the air inlet shutoff switch. Verify that the repair eliminates the problem. Result: The indications are not correct. There is a problem with the wiring between the 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 problem.
5. Check the Interlock for the Air Inlet Shutoff A. Verify that P1-62 is connected to the +Battery. J1/P1-62 is used for the transmission neutral switch. If a transmission neutral switch is installed, the transmission must be in neutral. B. Remove the air inlet shutoff switch. C. Turn the key switch to the ON position. D. Monitor the status for the air inlet shutoff switch while the two wires from the switch are connected.	P1-62 is connected to the +Battery.	Result: P1-62 is connected to the +Battery. Check the status for the "Transmission Neutral Switch" while the transmission is in neutral. The status should be "On". If the status is "Off", refer to Troubleshooting, "Neutral Switch Circuit - Test". Proceed to Test Step 6. Result: P1-62 is not connected to the +Battery. Connect P1-62 to the +Battery. Repeat Test Step 2.
6. Inspect Electrical Connectors and Wiring A. Turn the key switch to the OFF 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. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details. E. Check the harness and wiring for abrasion and for pinch points from the components back to the ECM.	Connectors are OK	Result: All the wires and connections are OK. Proceed to Test Step 7. Result: There is a problem with the wiring. 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 coupled. Verify that the repair eliminates the problem.

Show/hide table




Illustration 2	g00850138
Typical air inlet shutoff solenoid

Show/hide table

Table 3
Troubleshooting Test Steps	Values	Results
7. Check the Supply Voltage to the Air Inlet Shutoff Solenoid A. Turn the key switch to the ON position. B. Access the "Air Inlet Shutoff Relay Output" test on Cat ET. C. Measure the voltage across the two terminals of the air inlet shutoff solenoid. D. Activate the "Air Inlet Shutoff Relay Output" test. The output for the air inlet shutoff will be active for one second.	The voltage is within ±5 VDC of battery voltage	Result:The voltage is within ±5 VDC of battery voltage when the test is active. The ECM is properly controlling the relay for the air inlet shutoff solenoid, but the air inlet shutoff solenoid is not working. Replace the air inlet shutoff solenoid. Verify that the repair eliminates the problem. Result: The voltage is not within ±5 VDC of battery voltage when the test is active. The air inlet shutoff solenoid is not receiving the correct signal. Proceed to Test Step 8.
8. Check the Signal Voltage to the Relay A. Turn the key switch to the ON position. B. Access the "Air Inlet Shutoff Relay Output" test on Cat ET. C. Measure the voltage across the relay solenoid. The output for the air inlet shutoff system will be active for only one second. D. Activate the "Air Inlet Shutoff Relay Output" test.	The voltage is within ±5 VDC of battery voltage	Result: The voltage is within ±5 VDC of battery voltage when the test is active. The relay is receiving the signal from the ECM. Proceed to Test Step 9. Result: The voltage is not within ±5 VDC of battery voltage when the test is active. The relay is not receiving the signal from the ECM. Proceed to Test Step 11.
9. Check the Power Supply to the Relay A. Measure the voltage between the +Battery terminal of the relay and the engine ground.	The voltage is within ±5 VDC of battery voltage	Result: The voltage is within ±5 VDC of battery voltage. The relay is receiving power. Proceed to Test Step 10. Result: The voltage is not within ±5 VDC of battery voltage. There is a problem in the wiring between the relay and the +Battery terminal. Repair the circuit. Verify that the repair eliminates the problem.
10. Check the Output Voltage of the Relay A. Ensure that all of the circuits connectors are connected. B. Turn the key switch to the ON position. C. Access the "Air Inlet Shutoff Relay Output" test on Cat ET. D. Measure the voltage from the output terminal on the relay to the engine ground. The output for the air inlet shutoff system will be active for only one second. E. Activate the "Air Inlet Shutoff Relay Output" test.	The voltage is within ±5 VDC of battery voltage	Result: The voltage is within ±5 VDC of battery voltage. There is a problem in the wiring between the relay and the air inlet shutoff solenoid. Repair the circuit. Verify that the repair eliminates the problem. Result: The voltage is not within ±5 VDC of battery voltage. The relay is not sending power to the air inlet shutoff solenoid. Replace the relay for the air inlet shutoff. Verify that the repair eliminates the problem.
11. Check for a Short in the Wiring Harness between the Relay and the ECM A. Ensure that the key switch is in the OFF position. B. Disconnect the J2/P2 ECM connectors C. Disconnect the air inlet shutoff relay D. Measure the resistance between terminals P2-5 and P2-76. E. Measure the resistance between terminals P2-5 and P2-76.	The resistance is not an open circuit.	Result: The resistance is an open circuit. Proceed to Test Step 12. Result: The resistance is not an open circuit. There is a problem in the wiring harness between the ECM and the relay. Repair the circuit. Verify that the repair eliminates the problem.
12. Check for a Open in the Wiring Harness between the Relay and the ECM A. Ensure that the key switch is in the OFF position. B. Install a jumper wire between terminals 1 and 2 on the connector for the air inlet shutoff relay. C. Measure the resistance between terminals P2-5 and P2-76.	The resistance is a short circuit.	Result: The resistance is a short circuit. Proceed to Test Step 13. Result: The resistance is not a short circuit. There is a problem in the wiring harness between the ECM and the relay. Repair the circuit. Verify that the repair eliminates the problem.
13. Check the Relay Signal at the ECM A. Turn the key switch to the OFF position. B. Remove the terminals from P2-5 and P2-76. C. Turn the key switch to the ON position. D. Measure the voltage between terminals P2-5 and P2-76. The output for the air inlet shutoff system will be active for only one second. E. Activate the "Air Inlet Shutoff Relay Output" test on Cat ET. F. Turn the key switch to the OFF position. G. Return the wiring to the original configuration.	The voltage is within ±5 VDC of battery voltage	Result: The voltage is within ±5 VDC of battery voltage. The ECM is supplying the correct voltage. There is a problem in the harness between the ECM and the air inlet shutoff relay. Repair the circuit. Verify that the repair eliminates the problem. Result: The voltage is not within ±5 VDC of battery voltage. The ECM is not supplying the correct voltage. Replace the ECM. refer to Troubleshooting, "Replacing the ECM". Verify that the repair eliminates the problem.