‘05 5.4 3v, having a few problems with this truck as it wasn’t taken care of by previous owners. My injector 6 is not firing, no codes for #6 injector. Previous problem that I found was open circuit on 5& 6 coil. Injectors also weren’t working but I figured the computer might put it into limp mode as to not mess with the cats. Found the broken wires at the coil plug for both coils, when I started it up, both coils worked and the noid light tested good on #5 injector ( the computer in fact had shut it off)
injector 6 still does not fire, so I back pinned the plug and am getting my constant 12v but no ground signal. So I ohm tested the wire from the pcm to the injector plug and got 0.2 Ohms ( from my understanding the wire is complete with no breaks or corrosion)

backpinned the pcm (#37 left plug) to double check that it’s sending power an I found that it is not, it seems that it would need a pcm repair/ replace for that driver in the pcm.

So I had a few questions…

1. could the pcm not be sending power to the injector bc it’s still in limp mode? How could i fix that? Just resetting pcm?

2. what would’ve caused this problem if the wires aren’t shorted out or anything?( I don’t want to damage the next PCM

3. is there a place that is good for repair of the PCM? And what scanners would I need to program a new to me one if I went that route? ( I have forscan)

4. if the injector was mechanically stuck, would the pcm cut power to it to reduce potential harm?

5. If the tone ring was worn too much would the crankshaft sensor cause the computer to only skip 6th?

 

Limp mode will not affect one injector
It will lock the timing and adjust the rev limit
You put a "NOID" light in that injector connector
if it blinks while cranking or has a steady dim glow (fast blink) while running, replace the injector

 

B+ power is at the injector at all times key on, the processor grounds it for a certain amount of time (dewll) to fire the injector
I manually fire them while watching the fuel pressure drop
That helps me determine if any are faulty or not flowing properly
That is exactly what our old SBDS machined did at the dealer (Service Bay Diagnostic System)
It was a BIG very hard to use scope
Hard because you had to unplug the injectors and install the harness from the scope
Means on a 300-6 you had to pull the upper intake plenum off
Just about easier to make your own injector test fire apparatus

 

Pin 37 is the origination point for the ground signal to fire the injector and should not have 12 volts. Power, red wire, to all injectors (Hot in Run or Start) is through ignition key.

 

Jim boy

from what I read the pin should have 12 v key on and then once running it should be ground pulse.
still my problem is there is no resistance in the wire from pcm to injector which tells me the wire is good and I’m still not getting a pulse signal

 

manicmechanic007

i have already determined the pulse wire is good and not receiving signal

 

If the wire integrity from the pcm (pin 37) to the injector connector (pin 1) is good, and all other injectors are firing then it's very possible that the pcm is faulty, but before you make that call I recommend just a few easy steps

1- Unplug the injector an leave it unplugged (it could be shorted)
2- Check again for ground pulse
3- I no pulse in step 2 reset the pcm
2- Check again for ground pulse

If still no pulse from the pcm, you may have to make the call.

You can program it with Forscan, just going to need the beta software version (paid license) and 2 keys. Or, I've never done it but you can buy a preprogrammed pcm.