Thanks for the info Swoop helped a lot

found a service doc on this code
check your email

serial #is AT9003715 has Nissan 4cyl LPG system

serial number of truck?

the E-38 is:
LPG VAPORIZER DIAGNOSTIC RESULT SIGNAL

so there is some soft of fuel related problem

in one of the service grams i found it has a list of a troubleshooting guide to check related to this code but depending on the year/Tier level some of these may vary.

- Check fuel pressure.
- Replace the filter screen in the injection holder body under pressure sensor.
- Is fuel rushing past the injector body and into the intake?
- Fuel pressure readings low and tech adjusted the vaporizer. Unit is running fine.
- Found broken wires at the fuel pressure sensor. was reading 0.0 kpawith fuel lock jumped
out and engine running.
- Tech cleaned the fuel filter and cleared code.
- Resolution: screen plugged
- Check to see if the ECU was changed or the injection holder was changed. If the parts are mixed depending on fuel system, this code will set.
- Check injection holder filter screen if fuel pressure is too low.
- Check for fuel leaking into the balance line vacuum hose. (leaking vaporizer diaphragm).
- Check for raw fuel smell into the intake (listen for air noise when key on).