Thread: FUEL PRESSURE TOO HIGH/TOO LOW: 2005 TDV6 Discovery 3 S

If it's a common enough fault, logging with a Gap IID is a great way to see what is happening.
If it was the wiring as Graeme suggests it'll stick out in the data like a sore thumb. If it's not that, then watching the fuel pressure in conjunction with the volume and pressure control valves in the HPFP will give you more of an idea as to what might be happening.

The manual says : "The wires to the fuel sensor are monitored by the ECM for short and open circuit. The ECM also monitors the 5V supply.
If a failure occurs a fault is recorded in the ECM memory and the ECM uses a default fuel pressure value."

If it doesn't go outside of range far enough to log a code the ECM will use the "default" value and keep winding the pressure up to try and get it to rise. After a couple of seconds of that it'll fault.

From experience, the noise made by the injectors when exposed to maximum rail pressure is hellish. I did something silly when diagnosing my HPFP and jammed the PCV shut at idle, which pushed the pressure to maximum and it sounded like the injectors were going to experience a "rapid unexplained disassembly".

The wiring fault on the 4.4 only logs the P0088 DTC.