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.

Ok, it doesnt shut down after driving for 20minutes, only at an idle? And no codes at all are setting? If thats the case, that sounds like a thermal or heat related issue. Such as a sensor possibly getting hot and shorting out the 5v ref, it might be staying cool enough when youre driving. Ill take a look and see what Mode 6 data we could take a look at to give you some direction. Its what I do when im looking for something not bad enough to set a code but still cause a fault at some point.

Did you find anything else since your last posting?

Ok if youre still getting that weird code,
If this thing will cut out at just about 20min mark, I would be scoping both of the high pressure fuel rail sensors, if no scope, then monitoring and recording live data to see whats dropping out.
Get into both Fuel Rail Pressure sensor's signal wire(s) Or Data PIDs) and the Low (Fuel)Pressure Sensor, watch both of them when youre getting close to 20min and see if the signal spikes or drops out. They dont have the sensors labelled to good here, so I go by the sensors location Ill see on the fuel rail and then check by wire colors.
If theres an issue on the low pressure side, its going to effect the high side.
Another issue is we really dont even know if that code is accurate, obviously it looks odd to us both, so watching and trying to identify what dropped out at that time limit, you can graph the sensors signals with an Autel, and record the live data, so thats where I would start since we are unsure of that code. I want to see if theres any other info on it.
But retrace your steps, around the wiring harness that has been moved or bulk connectors taken apart, check pin fitment. That is common when it comes to heat related faults.

Well apparently a 00135 is a "Fuel/Rail System Pressure: Too Low". A P0087 can also set with it, another low pressure code. So concentrate on the fuel system pressure, start with checking the low side pressure stays good, theres a fuel pump control module for the low side if this info is correct.