Cause : Run disable comes when run enable signal is low. The message "Run enable signal is low" typically indicates that a system or process is not allowed to run because the "enable" signal is in a low state, meaning it's inactive or not at the required level for operation. 

Here's how to approach troubleshooting this issue:

1. Check Signal Connections: Ensure that all necessary connections for the "run enable" signal are properly established. This includes checking wiring, connectors, and any interface modules or devices involved in transmitting the signal.

2. Verify Control Logic: Review the control logic or software that governs the activation of the "run enable" signal. Check for any conditions or constraints that may prevent the signal from transitioning to a high state when needed. This could involve reviewing code in programmable logic controllers (PLCs), microcontrollers, or other control systems.

3. Inspect Sensors and Feedback Devices: If the "run enable" signal is dependent on sensor inputs or feedback from other devices, verify that these sensors are functioning correctly and providing the expected signals. Issues with sensors or feedback devices could prevent the system from enabling operation.

4. Check Safety Interlocks: Many systems incorporate safety interlocks that prevent operation if certain conditions are not met (e.g., doors closed, emergency stop buttons pressed). Ensure that all safety interlocks are properly engaged and that there are no faults or malfunctions preventing the system from entering the "run" state.

5. Power Supply and Grounding: Inspect the power supply to ensure that it's providing sufficient voltage and current to enable operation. Also, check for any grounding issues that could affect signal integrity.