System Operation Description:
Use this procedure in order to troubleshoot the air shutoff circuit or use this procedure if another procedure has sent you here. The Electronic Control Module (ECM) does not provide diagnostics for the circuits that are for the air shutoff system.
There are two conditions which can cause the ECM to activate the air shutoff:
Engine Overspeed – When an engine overspeed condition occurs the ECM energizes the air shutoff solenoid and the fuel injection is disabled.
System test – The overspeed verify switch can be activated by the operator in order to test the air shutoff system. The engine speed is then increased to 75 percent of the programmed overspeed setpoint and the ECM activates the air shutoff system. The ECM will then disable fuel injection.
Note: As the engine speed drops below 75 percent of the programmed overspeed setpoint, the injection is again enabled by the ECM. This functionality is not latched by the ECM and the functionality is disabled when the switch is turned off.
For some air shutoff systems, after the air shutoff mechanism has been tripped, a manual reset of the mechanism may be necessary.
Illustration 1 g01432430
Schematic for the air shutoff system
Test Step 1. Inspect the Electrical Connectors and the Wiring
- Remove electrical power from the ECM.
Illustration 2 g01139425
(1) J1/P1 connectors
(2) J2/P2 connectors
Illustration 3 g01210157
Typical air shutoff mechanism
(3) Terminals for the air shutoff solenoid
- Thoroughly inspect connectors (1) and (2). Also, thoroughly inspect any connections that are associated with the air shutoff circuit. Refer to Troubleshooting, “Electrical Connectors – Inspect”.
Illustration 4 g01432446
P1 terminals for the air shutoff system
(P1-32) Overspeed verify switch
Illustration 5 g01432448
P2 terminals for the air shutoff system
(P2-13) Air shutoff relay
- Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the air shutoff system.
- 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.
- Check the harness and the wiring for abrasion and for pinch points from the air shutoff solenoid to the ECM.
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.
- OK – The connectors and wiring appear to be OK. Proceed to Test Step 2.
- Not OK – The connectors and/or wiring are not OK.Repair: Repair the wiring and/or the connectors. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the problem is resolved.STOP