I have been battling this same issue. Recently purchased a 2014 Passat TDI 2.0 with around 51k miles. After driving it for close to 500 miles the light came on and I start researching and troubleshooting.
I started off simple with a new fuel filter realizing it was likely not going to fix anything but wanted to check for metal or debris. Filter was dirty but no metal found.
Then I replaced the fuel rail pressure sensor. I pulled the fuel rail out since I couldn’t get any tools on the sensor while it was in the car. Also, further reassured me since I found no metal in the rail when I cleaned it up. The intermittent issue persisted with the code popping when it so chooses.
I then added the new ground to the sensor but still spliced it into the harness, issue persisted. Thinking I may have created a ground loop, isolated the new ground just to the sensor. Still getting the blinking glow plug and P0193 code. I have half assed checked the harness and plan to look deeper once time allows. I was able to record the Fuel Rail Pressure Sensor trace along with the Commanded Fuel Rail Pressure. When the code comes on, the sensor reading is 200,000kpa steady while the commanded pressure is around 115,000kpa when accelerating (limited due to limp mode). Screenshot attached. If I drive for a while (less than a mile) the sensor starts showging good values again and an engine restart clears the code. If I restart while the value is 200,000kpa, then the code get locked and CEL gets illuminated.
Most of the time the code comes on when the engine is cool and code is active before engine starts. So a cold start in the morning, if I press the start button without cranking it is already active. It has come on a few times while driving. Seen in the second orange peak in the trace.
So, what does the sensor reading max (200,000kpa) likely indicate? A short in the harness crossing over or still a bad ground? Or complete lack of signal getting to the computer?
I unplugged the sensor this morning, ignition on, engine not running, and the trace did not change.