[redrag]

i doubt that the pcm fires the coils directly. there sould be a module that provides the ground to fire the coils conrtolled by the pcm. most pcms can't handle the current required to fire a coil

 

[Action]

The wiring to a coil from the pcm is just two wires. Both of those wires go back to the pcm. There is no module or relay between the coil and the pcm. At least that is the arrangement on my 2006 5.4l. That 12v small amp signal is stepped up to big voltage across the spark plug because of the coil on the spark plug.

>>>>>>>>>>>Action

 

[Fordman1]

The CEL comes on in key on position, but goes off during cranking. The tire inflation light blinks like 26 times an after 16 seconds in key on position the DEL light flashes like 8 times. I pulled com relay and am going to get another
I'll probably switch with another to test, looks like same relay(seeing they are $48).

 

[Action]

My guess is you have a good pcm because there is a 12v signal to the coils. However the pcm does not see a signal to fire off the coils. If I am not mistaken, that signal is from the crank or cam sensor.

I am pretty sure you have replaced those. Assuming that is the case, either the replacements are defective or there is an issue with the wiring from those sensors back to the pcm. Those sensors get a 5v signal and modify that base signal from the pcm back to the pcm. The pcm then makes the decision which coil to light up.

The shop manual has a good diag routine for no start and other conditions. I am sorry this issue has not been resolved.

:>>>>>>>>>>>>>>>>Action

 

[Fordman1]

I am too. Actually the repair guides I am using, have 2, are relatively minimal. I didn't figure the 12v to coil came from pcm seeing 12v constant, I was figuring came directly from junction block. I figured, it doesn't say in manual, that pcm had to break ground for plugs to fire. Yes I've replaced crank sensor twice, and cam sensor. I had to set time when reinstalling 2nd crank sensor and I even pulled valve cover and verified that had correct cam in correct placement to trigger sensor as well as double checking cam timing. The tests I seen for crank sensor said nothing about 5v feed, they only said that it should create an ac voltage, so I didn't think that it would have feed voltage. I will double check 5v as I didn't really want to poke holes through my crank sensor wiring to check for generated ac voltage. This car did sit for months while awaiting us to afford all the parts, that is why I was wondering if pcm could do something while unplugged for months, but they state that anti theft causes no crank situation. You have access to which wire on pcm comes from crank sensor?

 

[Fordman1]

Ok as I suspected for you trying to use this in the future, the hot for the coils comes from the PCM relay in the power distribution box, hence constant 12v. The ground side comes from the PCM, which makes or breaks for plugs to fire.

 

[Fordman1]

I have tested the ground side of the coil wires and the ground is not breaking. I guess the only test for the crank sensor is the ac voltage test, but seeing this is the 2nd new one(unless I bought 2 previous ruined crank sensors) I would have to presume that it is reading the sprocket on the crank pulley and sending signal to the PCM.....and seeing I even three a new cam sensor on for good measure, that might support my theory. The only other thing I've been wondering if from setting months without power if PCM flashing would help, but I can't find any support of that theory.

 

[Action]

A disconnected PCM does not make the PCM not work. The PCM may have to re-learn the engine and sensor norms however the engine should still run.

There should be a 5V signal from the PCM to all sensors.

Has the crankshaft sensor been replaced?

>>>>>>>>>>>Action

 

[Fordman1]

Not 5v to the crank sensor as that produces an ac voltage for the PCM. As just stated Crank sensor replaced twice.

 

[Action]

I am out of solutions. If it were me I would go through the no start routine in the Ford shop manual. That section has a good step by step diagnosis path.

>>>>>>>>>>>>Action

 

[redrag]

don't know if things changed in 07, but according to wiring diagram for 06, crank sensor is the same as a distributer pickup. if you unplug it and probe the connecytor while cranking you can verify output

 

[Fordman1]

I think that one side is a ground probably from PCM and generates ac voltage signal for PCM to read and sense and pulse ground wire at coils to fire. Seeing I've replaced crank sensor twice I'm still thinking PCM bad.

 

[Fordman1]

The wiring to a coil from the pcm is just two wires. Both of those wires go back to the pcm. There is no module or relay between the coil and the pcm. At least that is the arrangement on my 2006 5.4l. That 12v small amp signal is stepped up to big voltage across the spark plug because of the coil on the spark plug.

>>>>>>>>>>>Action

This is not correct in this case and I'd have to side with Redrag, the 12v comes from PCM relay in junction box. It gives it constant 12v on the hot wire on coil.