Recommended Procedure:

WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2004 Ford RV Cutaway, 2004 Ford Pickup, 2004 Ford F550 Super Duty, 2004 Ford F450 Super Duty, and 2004 Ford Excursion. However, it is still accessible from the selected car via links, so may be relevant.

Connect the scan tool.
Key on, engine off.
Access and monitor the ICP and IPR PIDS while cranking the engine.

NOTE: A CKP signal is required before the IPR is commanded above 14%.

If the ICP does not meet the minimum specification of 3.5 mPa (500 psi), the injectors will not be enabled by the PCM because of insufficient rail pressure.

If the IPR duty cycle is greater than 14%, ICP pressure should increase above 3.5 MPa (500 psi) provided that the IPR valve is not stuck open, the high pressure pump is building pressure and there is not an injection control pressure leak between the high pressure pump and the injectors.