KNOB AS-WIPER SWITCH 7T9302 - Caterpillar

System Operation Description:The Secondary Electronic Control Module (ECM) has the ability to stop the engine by cutting off the air supply to the engine in an emergency situation. The ECM activates two relays which energize the two air shutoff solenoids. The solenoids trip the air shutoff valves.There are two conditions which cause the engine control to activate the air shutoff relay. The first condition occurs when the operator initiates a remote shutdown. If the remote emergency stop button is activated the fuel is shut off and the air shutoff relay is activated. The Secondary ECM will hold the relays active for 1.5 seconds. The second condition occurs for an engine overspeed. The engine overspeed could be an actual overspeed condition or a simulated overspeed condition. The overspeed condition can be simulated by activating the Overspeed Verify switch. The Overspeed Verify switch is located inside the instrument panel in the upper left corner.The air shutoff relay can also be activated without the aid of the ECM. When the emergency stop on the instrument panel is depressed, the air shutoff relay is activated. The air shutoff timer will allow the air shutoff relay to deactivate after 2.5 seconds in order to prevent damage to the air shutoff solenoids.Regardless of the reason for activation, the Engine Control Switch (ECS) must be turned to the OFF/RESET position for three seconds in order to reset the ECM and the air shutoff timer.
Illustration 1 g00903323
Typical air shutoff circuitNote: The Engine Control Switch (ECS) is mounted within an instrument panel that is located on the right side of the engine. The ECS is locked into the AUTO position with a pin. The pin must be removed in order to perform this test. After performing this test, ensure that the ECS is placed in the AUTO position and that the locking pin has been reinstalled.Test Step 1. Check for Connector Damage.
Verify that the circuit breakers are not tripped.
Turn the circuit breaker for the battery to the OFF position.
Turn the ECS to the OFF/RESET position.
Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.
Check the ECM connectors (allen head screw) for the proper torque of 6.0 N m (55 lb in).
Check the customer connectors (allen head screw) for the proper torque of 2.25 0.25 N m (20 2 lb in).
Check the harness and the wiring for abrasion and pinch points.Expected Result:All connectors, pins, and sockets are coupled and/or inserted, and the harness and wiring should be free of corrosion, abrasion, or pinch points.Results:
OK - The connectors and wiring are okay. Proceed to test step 2.
Not OK - The connectors and/or wiring are not okay.Repair: Repair the connectors or wiring and/or replace the connectors or wiring.STOPTest Step 2. Test the Air Shutoff System.
Turn the circuit breaker for the battery