2005 Isuzu NPR 5.2L Diesel with engine code P0091

Question

P0091 code sets on my 2005 Isuzu NPR, I can run the engine and unplug the regulator and get a weak 12-volt test light on the power supply wire. I don't have a wiring diagram and don't know if this is normal.

Answer 1

This code indicates an issue with the fuel pressure sensor. Here is some info for you.

P0091 ISUZU - Fuel Pressure Regulator Solenoid 1 Control Circuit Low Voltage
Read more: https://www.autocodes.com/p0091_isuzu.html