STUD 8T7044 - Caterpillar

System Operation Description:The customer's emergency stop switch sends a signal to the Electronic Control Module (ECM). The signal is used to determine if the emergency stop switch is active. The emergency stop switch is active when the switch is in the open state and the signal is held high. The emergency stop switch is inactive when the switch is in the closed state and the signal is at a low potential. The signal is routed through the air shutoff switches at the air shutoff valves. When the air shutoff valves are activated, the air shutoff switches open. When the air shutoff switches open, the ECM sees the open on the signal wires. The ECM will stop the signals to the injector solenoids.The harness wiring from the air shutoff switches has two wires to the engine shutdown inputs of the ECM. If the ECM is powering up and one of the signals from the air shutoff switches is in a different state from the other signal, the ECM knows that one of the signal wires is faulty. If one of the signal wires from the air shutoff switches is in a different state from the other signal wire, the ECM will generate a diagnostic code that remains active until power to the ECM is cycled. The ECM will allow the crank cycle to begin if the signals are opposite of each other. The ECM will allow the engine to be started in this state.The ECM initiates an emergency stop shutdown only when both signals are in the open state during engine operation.For safety, the ECM will not allow the starting sequence to begin after the emergency stop switch is activated. Two switches at the air shutoff valves will open when the air shutoff valves close. In order to restart the engine, the following conditions must be met.
The initial emergency stop condition must be resolved.
The air shutoff valves must be reset to the OPEN position.
The remote emergency stop switch must be reset to the OFF position.
The Engine Control Switch (ECS) must be turned to the OFF/RESET position.Note: Before performing this test, ensure that the air shutoff valves are in the OPEN position.
Illustration 1 g00975798Test Step 1. Check for Connector Damage.
Turn the circuit breaker for the battery to the OFF 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 connector that are associated with the circuit.
Check the ECM connector (allen head screw) for the proper torque of 2.25 N m (20 lb in).
Check the customer connector (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 for pinch points. Expected Result:All connectors, pins, and sockets are completely coupled and/or inserted. The harness and the wiring should be free of corrosion, of abrasion or of