SEAL-O-RING 4D9986 - Caterpillar

System Operation Description: When the local emergency stop switch on the instrument panel is depressed, the coils of relay "R4" and relay "R4A" are energized. The contacts of relay "R4" keeps the coils of relay "R4" and relay "R4A" energized until the Engine Control Switch (ECS) is cycled to the OFF/RESET position. The contacts of relay "R4A" energizes the coils of relays "R2" and "R2A". When relays "R2" and "R2A" are energized, power is removed from the engine's primary Electronic Control Module (ECM) and the engine's secondary ECM. The primary ECM and the secondary ECM will power down. The injection signals to the injector solenoids will stop. The emergency stop lamp on the instrument panel will illuminate.The contact of relay "R4A" also supplies power to terminal 1 of the connector for the timer. When power is applied to terminal 1 of the connector for the timer, the timer will activate. The timer outputs 24 VDC to terminal 4 of the connector for the timer for 2.5 seconds. The 24 VDC from terminal 4 of the connector for the timer is applied to the coil of the air shutoff switch (ASOS). The contact of the "ASOS" switch energizes the air shutoff solenoids. The timer will output voltage to the coil of the "ASOS" switch for approximately 2.5 seconds. The "ASOS" switch will then deactivate removing power to the air shutoff solenoids. This prevents damage to the air shutoff solenoids. A normally open switch at the air shutoff valves will close when the air shutoff solenoid activates the air shutoff valve. The switch input to the ECM notifies the ECM that the air shutoff valves are closed. The ECM will not send injection signals to the injector solenoids until the switch inputs from the air shutoff valves indicate that the valves are open.Relay "R3A" and relay "R3" are energized at the same time as the "ASOS" switch through terminal 3 of the diode assembly. Terminal 3 of the diode assembly will energize relay "R3A" and relay "R3" for 2.5 seconds. The relays "R3A" and "R3" will de-energize after 2.5 seconds. The overspeed indicator on the instrument panel will illuminate for 2.5 seconds.In order to start the engine after an emergency stop condition, the ECS must be turned to the OFF/RESET position. This resets the ECM and the air shutoff timer. In addition to turning the ECS to the OFF/RESET position, the operator must manually open the air shutoff valves before starting the engine.
Illustration 1 g01029797
Typical exampleTest 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