Originally Posted by pirschwagon

Here is a process for testing the P1316. Perhaps you can narrow it down further.

DIAGNOSTIC TROUBLE CODE (DTC) P1316 INDICATES THAT CODES ARE STORED IN THE IDM

Possible causes:

a. Injector(s) or circuit(s)

b. Open or shorted IDM enable circuit

c. Open/short in EF circuit

d. Open/short in FDCS circuit

e. IDM relay

f. IDM powering circuits

g. IDM

h. PCM

Check for other codes.

Key on, engine off. (KOEO)

Perform KOEO On-Demand Self-Test.

P1316 OR P1670, CHECK FOR AN INTERMITTENT OPEN CIRCUIT

KEY OFF.

Install breakout box, leave PCM disconnected.

Disconnect IDM.

Check for intermittent open in the following circuits:

Measure resistance on (FDCS) Circuit 821 (BR/O) between IDM connector Pin 17 and PCM Test Pin 95.

Measure resistance on (EF) Circuit 818 (GY/W) between IDM connector Pin 4 and PCM Test Pin 48.

Grasp the harness close to the IDM connector. Wiggle, shake the harness while working your way back to the PCM, while looking for a spike on the DVOM.

Description The IDM provides the EF output signal to the PCM to confirm that proper timing/duration of fuel delivery command signal (FDCS) was received. Additionally, the EF signal is used to send diagnostics of the IDM and injectors (electrical) to the PCM.

DTC Description

P1668 = PCM-IDM diagnostic communication error

P1670 = Electronic feedback signal not detected

P1316 = Indicates that IDM DTCs are stored within the IDM

DTC P1668 and P1670 indicates that a communication error has occurred between the PCM and the IDM.

Possible causes:

a. Open fuse

b. IDM relay

c. Open or shorted IDM enable circuit

d. Open/short in EF circuit

e. Open/short in FDCS circuit

f. IDM powering circuits

g. PCM

h. Check for other codes.

KOEO:

Perform KOEO On-Demand Self-Test and retrieve Continuous DTCs.

CHECK CIRCUIT 818 (GY/W) FOR OPEN

Install breakout box; leave PCM disconnected.

Disconnect the IDM harness connector.

Measure resistance on Circuit 818 (GY/W) between PCM Test Pin 48 and IDM harness connector Pin 4.

Key on, engine off. Measure for voltage on Circuit 818 (GY/W) between PCM Test Pin 48 and battery ground.

Turn ignition switch to OFF. Measure resistance on Circuit 359 (GY/R) between PCM Test Pin 91 and IDM connector Pin 2.

Originally Posted by David7.3

Note these were taken on a fully warmed up truck. At idle ICP 590psi, IPR 13%. cruise light ICP 1200psi, IPR 22%, and under load ICP 1850psi, IPR 33%. I took the fuel filter out and to my surprise everything was clean, My fuel light just came on thinking I was going to drop the tank and clean it. So I removed the driver side valve cover and ohmed all the injectors at the engine connection on the drivers side, all injectors were 4.5 ohms, as the truck cooled down the ohms dropped as well. I disconnected the fuel supply to the drivers head and unscrewed the FRx hose, ran a half a gallon of diesel at the supply and caught it at the end with a long hose, I didn't know there was a screen in the fitting that goes in the head, "that was clean" I ran it thru at 65 psi and it came out just as clean as it went in. Now I am having second thoughts about this being a dirt problem. I all ways use ford fuel filters, dont want to have to worry about the top only fitting one type, so I have 3 ford filters with me at all times. my tool box is a Ford man's dream, spare belts, all fluids, filters, coolant, fuel and oil. shovel, waders you name it I got it in there. So tomorrow I am going to pull the injectors and go from there. Thanks for everyone's help.