C7 and C9 Industrial Engines Troubleshooting – Air Shutoff – Test

For some air shutoff systems, after the air shutoff mechanism has been tripped, a manual reset of the mechanism may be necessary.

Illustration 1 g01165526
Schematic for the air shutoff system

Table 1
Troubleshooting Test Steps	Values	Results
1. Inspect the Electrical Connectors and the Wiring A. Remove electrical power from the ECM. B. Verify that the air shutoff mechanisms are set to the OPEN position. C. Thoroughly inspect the connectors. Also, inspect the connections at the air shutoff solenoid. Refer to Troubleshooting, “Electrical Connectors – Inspect” for more information. D. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the air shutoff system. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the air shutoff system. E. Check the allen head screw on each ECM connector for the proper torque. Also, check the allen head screw on the customer connector for the proper torque. Refer to Troubleshooting, “Electrical Connectors – Inspect” for the correct torque values. F. Check the harness and the wiring for abrasion and for pinch points from the air shutoff solenoid to the ECM.	Electrical Connectors and Wiring	Result: The electrical connectors and wiring are OK.Proceed to Test Step 2. Result: The electrical connectors are NOT OK. Repair: Repair or replace the damaged parts and return to service.

Illustration 2 g01165714
Location of the test lamp

Table 2
Troubleshooting Test Steps	Values	Results:
2. Test the Operation of the Control Solenoid for the Air Shutoff RelayA. Turn the keyswitch to the OFF position. B. Remove the wire from the output of the air shutoff relay. C. Connect a test lamp between the output of the solenoid for the air shutoff relay and engine ground. D. Start the engine. E. Activate the overspeed verify switch. F. Monitor the test lamp while you increase the engine speed past 75 percent of the programmed overspeed setpoint. G. Stop the engine. H. Remove the test lamp from the circuit. Restore the wiring to the original configuration.	Control Solenoid	Results: The test lamp illuminated. The air shutoff relay is operating correctly. Proceed to Test Step 3.Results: The test lamp did not illuminate. No voltage is present at the output of the relay. Proceed to Test Step 4.
3. Test for Voltage at the Air Shutoff SolenoidA. Ensure that the keyswitch is in the OFF position. B. Disconnect the wire from the positive terminal of the air shutoff solenoid. C. Connect a test lamp between the wire for the positive terminal of the air shutoff relay and engine ground. D. Start the engine. E. Activate the overspeed verify switch. F. Monitor the test lamp while you increase the engine speed past 75 percent of the programmed overspeed setpoint. G. Stop the engine.	Voltage	Results: The test lamp illuminated.Repair: The voltage is present at the air shutoff solenoid. Check for continuity of the ground circuit for the air shutoff solenoid before proceeding. If the ground circuit is OK, replace the air shutoff solenoid. Verify that the problem is resolved. STOP Results: The test lamp did not illuminate. Repair: System voltage was not present at the air shutoff solenoid. There is a problem in the wiring between the output of the air shutoff relay and the input of the air shutoff solenoid. There may be a problem in a connector. Repair the wiring and/or the connector. Replace parts, if necessary. Verify that the problem is resolved. STOP
4. Test the Control Input Voltage at the Air Shutoff RelayA. Ensure that the keyswitch is in the OFF position. B. Disconnect the wires from the control input of the air shutoff relay at the relay. C. Connect the test lamp between the two control wires. D. Start the engine. E. Activate the overspeed verify switch. F. Monitor the test lamp while you increase the engine speed past 75 percent of the programmed overspeed setpoint. G. Stop the engine.	Input Voltage	Results: The test lamp illuminated. Control input voltage is reaching the relay. Proceed to Test Step 6.Results: The test lamp did not illuminate. Repair: The voltage from the ECM was not present at the coil of the air shutoff relay. Restore the wiring to the original configuration. Proceed to Test Step 5.

Table 3
Troubleshooting Test Steps	Values	Results
5. Check the Output Voltage for the Air Shutoff Relay at the ECMA. Ensure that the keyswitch is in the OFF position. B. Disconnect the P1 ECM connector. C. Fabricate a jumper wire that is long enough to reach from the P1-54 ECM connector to engine ground. Crimp a connector socket to one end of the jumper wire. D. Remove the wire from terminal location P1-54 (overspeed verify switch) at the ECM connector. Insert the jumper wire into this terminal location. E. Fabricate two other jumper wires that can be used as test leads at the ECM connector. Crimp a connector socket to one end of each jumper wire. F. Remove the wires from terminal locations P1-11 (air shutoff solenoid) and P1-67 (solenoid return) at the ECM connector. Insert one of the jumper wires into each of these terminal locations. G. Connect the J1/P1 ECM connectors. H. Connect the loose end of the jumper wire that is in terminal location P1-54 to the engine ground stud. I. Connect the leads of the voltage test lamp to the loose ends of the other two jumper wires that are in the P1 ECM connector. J. Start the engine. K. Monitor the test lamp while you increase the engine speed past 75 percent of the programmed overspeed setpoint. L. Stop the engine.	Output Voltage	Results: The test lamp illuminated.Repair: The ECM is operating correctly. Perform the following procedure: 1. Verify the continuity of the ground circuit for the overspeed verify switch. 2. Isolate the overspeed verify switch from the circuit. Close the switch and measure the continuity across the switch. Open the switch and measure the continuity across the switch. 3. Verify the continuity of the circuit between the overspeed verify switch and the P1 ECM connector. 4. Restore the wiring to the original configuration. If the overspeed verify that switch is OK and the circuit has continuity from the P1 and the engine ground stud, there is a problem in the wiring between the P1 ECM connector and the air shutoff relay. Repair the circuit connectors or wiring and/or replace the circuit connectors or wiring. Verify that the problem is resolved. STOP Results: The test lamp did not illuminate. Repair: Restore the wiring to the original configuration. There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, “Replacing the ECM”. STOP

Illustration 3 g00761537
Diode leads

Table 4
Troubleshooting Test Steps	Values	Results
6. Test the Diode for the Control CircuitA. Disconnect the air shutoff relay’s control wires at the relay. B. Remove the diode from the air shutoff relay. C. Select the “Diode Check” function on a digital voltmeter. D. Place the red lead of the digital voltmeter on the diode at location (A). Place the black lead of the digital voltmeter on the diode at location (B). E. Measure the voltage drop across the diode.	Diode	Results: The voltage drop across the diode is less than 1 V. The voltage drop across the diode is OK. Proceed to Test Step 7.Results: The voltage drop across the diode is greater than 1 V. Repair: The diode is damaged. Replace the diode. Verify that the problem is resolved. STOP
7. Test the Diode for Current FlowA. Reverse the position of the leads for the digital voltmeter. B. Measure the voltage drop across the diode.	Current Flow	Results: The digital voltmeter indicates an OL across the diode for this measurement. The diode is OK. Proceed to Test Step 8.Results: The digital voltmeter does not indicate an OL across the diode. Repair: The diode is damaged. Replace the diode. Verify that the problem is resolved. STOP

Illustration 4 g01165747
Location of the test lamp

Table 5
Troubleshooting Test Steps	Values	Results
8. Check the Voltage from the Keyswitch to the Voltage Input of the Air Shutoff Relay A. Ensure that the keyswitch is in the OFF position. B. Remove the wire at the voltage input of the air shutoff relay. C. Connect the test lamp between the wire for the voltage input and the terminal for the voltage input at the air shutoff relay. D. Turn the keyswitch to the ON position. E. Check the test lamp. F. Turn the keyswitch to the OFF position.	Voltage	Results: The test lamp illuminated. Repair: The relay contacts are not passing the secondary voltage to the circuit for the air shutoff solenoid. Replace the air shutoff relay. Verify that the problem is resolved. Results: The test lamp did not illuminate. Input voltage is not reaching the relay. Proceed to Test Step 9.
9. Check the Harness between the Keyswitch and the Air Shutoff Relay A. Turn the keyswitch to the OFF position. B. Remove the wire from terminal R (keyswitch) of the keyswitch. C. Turn the keyswitch to the ON position. D. Measure the voltage between terminal B (+Battery) of the keyswitch and engine ground. E. Measure the voltage between terminal R (keyswitch) of the keyswitch and engine ground. F. Turn the keyswitch to the OFF position.	Wiring Harness	Results: Voltage is present on terminal B and terminal R at the keyswitch. Repair: If voltage is present on terminal R, repair the wire between the keyswitch and the air shutoff relay. Verify that the breaker is not tripped. Return all wiring to the original configuration. Verify that the problem is eliminated. STOP Results: Voltage is not present on terminal B at the keyswitch. Repair: If voltage is not present on terminal B, repair the wire between the +Battery and the keyswitch. Verify that the breaker is not tripped. Verify that the battery disconnect switch is operating correctly. Check the battery’s no-load voltage. Return all wiring to the original configuration. Verify that the problem is eliminated. Results: Voltage is not present on terminal R at the keyswitch. Repair: If voltage is present on terminal B of the keyswitch but not present on terminal R, replace the keyswitch. Return all wiring to the original configuration. Verify that the problem is eliminated. STOP

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