JOINT GP-UNIV- 4974982 - Caterpillar

Introduction
Do not perform any procedure in this Special Instruction until you read this information and you understand this information.This Special Instruction provides potential causes of the emergency stop switch in relation to engine shutdown and to starting failure.Emergency Stop Switch's Circuit
The Engine Control Module (ECM) is designed to receive a common ground emergency stop signal at the ECM terminals J1-2 and J1-24. When the ECM receives a signal that the emergency stop switch is activated, the ECM activates the air shut off relay. The ECM also sets the duration of fuel injection to 0 seconds, regardless of whether the engine is running. The emergency stop state is latched until the ECM is power cycled.The potential at ECM terminals J1-2 and J1-24 should always be at the same state. The state of the terminal connections dictate the following ECM actions:
When both inputs are high (not ground), the ECM assumes the emergency stop switch is activated.
When both inputs are low (grounded), the ECM assumes the emergency stop switch is not activated. The engine will start.
If the inputs are different from each other on power up, the ECM senses that one of the inputs is faulty and a diagnostic code will be active until the ECM is powered down. The engine will start.
If the inputs develop different states during engine operation, the engine will continue to run. The ECM senses that one of the inputs is faulty and a diagnostic code will be active until the ECM is powered down.Causes for Failure to Start or for Engine Shutdown
If both inputs become high, the engine will not start. This can be caused by activation of the emergency stop and by wiring for the emergency stop that is missing, loose, broken, and/or frayed. The engine will only start if one or both inputs are at low ground.No Indicator Light
The ECM sends the emergency stop signal. The emergency stop signal is in a different data register message than the EMCP monitors. When this happens the EMCP will not display a fault, and the operator does not receive a indicator light. If this occurs, the ADEM software needs to be updated.Recommended Maintenance Procedures
Check continuity of wiring between the emergency stop switch (normally closed contact) and the ECM (terminals J1-2 and J1-24). This includes terminal connections at the emergency stop switch, at the terminal blocks, and at the ECM. Also, ensure that tension on the wires at the connection points is relieved in order to help minimize potential loss of the connection.If continuity exists, there is not an issue and the operator should see the emergency stop signal.If no continuity is present, check all the wiring for loose connectors or for worn connectors. If necessary, repair the wiring.Optional Procedure
The following procedure adds the capability for the transmission of a backup signal. Modify the wiring from the emergency stop switch to the ECM. The original wiring from the emergency stop to the ECM terminals J1-2 and J1-24 is accomplished by one wire. The one wire is separated