RING 1438138 - Caterpillar

System Operation Description:This procedure checks the circuits for the air shutoff system. 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 - The first condition occurs when the ECM detects an engine overspeed condition. The ECM energizes the air shutoff solenoid and the fuel injection is disabled. The air shutoff system is latched by the ECM until the keyswitch is cycled.System test - The second condition occurs when a test of the air shutoff system is performed. The overspeedverifythat switch can be activated by the operator to perform this test. The engine speed is then increased to 75 percent of the programmed overspeed setpoint. The ECM activates the air shutoff system as the engine speed exceeds 75 percent of the programmed overspeed setpoint. The ECM energizes the air shutoff solenoid and fuel injection is disabled. The air shutoff system is latched by the ECM until the keyswitch is cycled.Note: If the "Air Shutoff" parameter is set to "Not Installed", the functionality for the overspeed verify switch remains operational. If the switch is activated during engine operation, the ECM will disable injection for any engine speed over 75 percent of the programmed overspeed setpoint. 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 g01165526
Schematic for the air shutoff system
Illustration 2 g01167488
ECM connectors (typical example)
(1) J1/P1 ECM connectors
Illustration 3 g01146383
Customer connector (typical example)
(2) J61 customer connector
Illustration 4 g01210157
Air shutoff mechanism
(3) Terminals for the air shutoff solenoid
Illustration 5 g01212805
Terminal locations at the P61 customer connector that are associated with the air shutoff system
(4) Air shutoff relay
(5) Return
(40) Overspeed verify switch
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 connectors (1) and (2). Also, thoroughly inspect connections (3) at the air shutoff solenoid. Refer to Troubleshooting, "Electrical Connectors - Inspect".
C. Thoroughly inspect connectors (1) and (2). Also, thoroughly inspect connections (3) at the air shutoff solenoid. Refer to Troubleshooting, "Electrical Connectors - Inspect".
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.
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 connectors and wiring appear to be