Hey there, fellow night-shift warrior! I've been in that exact 2 AM panic situation more times than I'd like to admit. When the line goes down and the error codes are giving you cryptic messages, here's my systematic approach that's saved my bacon more than once:

First, I take a deep breath and start with the basics - safety first, then power. I check if there's power to the PLC rack and servo drives. No power? That's your starting point. If there's power, I look at the PLC status lights - are they solid, blinking, or off? This tells me if the PLC is running, in fault, or has communication issues.

Next, I check the servo drives. Most have diagnostic LEDs that show status - green for good, red for fault, flashing patterns for specific errors. Even if the error code is ambiguous, the LED pattern often gives better clues. I also feel the servo motor - is it hot? Overheating can cause weird faults.

For mechanical issues, I listen and look. Is there unusual noise? Can I turn the mechanism by hand (with power off, of course)? Mechanical binding often shows up as servo overload faults. I check for loose couplings, worn bearings, or physical obstructions.

My golden rule: start simple, work toward complex. Check physical connections first (cables, connectors), then power, then communication, then programming. And always document what you find - it helps the day shift and creates a history for future troubleshooting.

Remember, ambiguous errors often mean multiple issues or cascading failures. Take it step by step, and don't be afraid to call for backup if you're stuck. Better to get the line running with help than to waste hours going in circles!