CODE 00135 fuel rail pressure too low?

Hello, yeah you should be able to see the "Fuel Pressure" reading that will be somewhere around 60-80psi, this is the low side pressure. The High pressure fuel spec at idle is usually somewhere between 400-1800psi depending on engine's load and demand. What is the exact code number you are getting? The code's extra numbers (more than just the 4 digits) can give a little more direction as to what the ECM is coding for. Are you getting any other codes? Ill get the wiring diagrams so you can check the 5v reference at the high pressure fuel sensor.

Just a 0035 code? Yeah that code isnt listed in that manner through All data. This is a pretty complex system. I see HP fuel pumps for each bank.
With your scan tool are you looking into the live data on the manufacturers side of the scanner? If so try looking under global OBD 2 live data and see if it lists a low pressure and high pressure readings.
There is a flow chart for checking the High Pressure fuel sensor ill post here. If this is the actual fault, but issues with the low side of the fuel pressure system will obviously cause issues on the high pressure side since its the feed for it.
These diagrams are for checking the fuel system before checking the high pressure system. Ill post the high pressure testing next. Both pressure sensors work on a 5volt reference.

This is the service info for checking the high pressure fuel sensor. You may want to try a different scan tool as well, and see if the code numbers change. Just curious if theres any difference. You use Autel scan tools correct?

There definitely should be data PIDs for both the high and low pressure fuel systems.