randel1

I am working on a 2004 F-150 5.4 3V. I was getting 2 codes that told me that cyl. 3 and 4 ignition coil or spark plug was not firing. I decided to replace the plugs and of course had to extract 2 out of the 8 but managed without damage to cylinder head threads. I replaced all plugs and tested the coils and plugs prior to install, all checked good. I am now experiencing P 0201, P0204, P0206, and P0207 error codes which are injector failure codes. Further testing revealed that I was not getting ground switching to those injectors so they were not cycling on and off. The injectors test good when swapped with those that are are operating properly. I suspected that the PCM was defective so I had it checked out and the test results showed no problem with the injector circuits. A continuity test on the wiring from the P M to the injector tested good. So now what, any suggestions would be appreciated.
I posted this earlier and had no reply, I probably put it in the wrong place or did something else stupid, still trying to figure how to navigate this site.

Marc D

The codes you're still throwing are injector codes as I'm sure you know by now. You have confirmed they are all good so it leads me to believe you have a wire harness problem. First I would check the harness that loops around the injector rail and if all good then I would check the harness blocks on the firewall (low on the drives side) that bolt to the matching plug that connects the body to the motor harness. There should be 3 blocks (plastic) with one bolt each holding them in place. Check for loose bolts, damage to the pins and corrosion. Good luck

randel1

Thanks Marc D
Actually, I have +12 VDC to the injectors but I am not getting the ground pulse to actuate the solenoid within. The wiring harness rings out Ok back to the PCM which is located on the firewall passanger side. Male and female contacts all look good. It almost acts as if it is stuck in the limp mode and will not reset.

RLXXI

Did you check continuity of the ground or signal wires from the injector harness plug to the harness plug at the pcm? If continuity is good and not shorted to power or ground then you have a bad pcm.


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randel1

Thanks Rnlcomp
I did check the continuity of the ground wires back to the PCM and they all checked good. This also led me to believe the PCM was bad so I sent it in for testing and repair. It was checked out and said to be in good working order and passed all tests.

RLXXI

Did you check continuity of the injector signal wire straight to ground? If those wires are shorted to ground the injectors will default wide open. I've seen it happen many times after critters chewed the harness under the upper intake manifold plenum.



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randel1

Thanks again Rnlcomp
I have connected a test light between pin 2 and gnd. and get 12 VDC on all injectors. When connected between pin 1 and gnd. the test light blinks when the gnd path is triggered on the injectors that are working. However on 1, 4, 6 & 7 I get no blink, just steady on. I will go through the continuity check again tomorrow to compare actual resistance of the wires. At the same time I will give the harness a good visual inspection. I think it is rare that I would have 4 injectors not firing and I have been looking for something that may be common to those injectors. I have limited electrical schematics and am not sure where the trigger source is located that tells the PCM to supply the ground in order to complete the circuit.

RLXXI

You will always have 12v to each and every injector key on, the pcm pulses the ground (pulse width) to deliver the proper amount of fuel depending on engine load, engine temp, mass air, etc.

The system you are working with should be sequential meaning the pcm fires each and every injector in firing order, just like the ignition system delivers spark to each cylinder when it needs it.

Each injector has a separate ground pulse wire from the pcm.

The only thing all injectors have in common is the 12v to operate. Since you say only some of the wires you have probed blink and others do not, you have isolated at least some of the circuits that need attention.

Tried to pull up the wiring schematic but something's wrong, not sure what but I'll figure it out........eventually. I'm betting on critter damage.

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randel1

I'll get on it first thing in the A.M. and post my findings. Thanks Rnlcomp

randel1

Well, I got on it again early this A.M. I ckd' continuity from pin 2 of all injectors back to the connector at the PCM all ckd. less than .7 ohms. I also checked for pin 2 to ground and they all read infinity ohms. With ignition on, all pin 1's have 12VDC. I got it started once this morning to move it inside to work on it, It was only hitting on 3 or 4 cyls., then disconnected the battery to do my pin outs. Gave the wiring harness a good visual inspection and there was no evidence of critter damage. Connected everything back up and ckd for 12V at pin 1 on injectors all Ok now I cannot get it to run long enough for error codes to register, had to stop and put charger on battery.