Cranks for 2 seconds and quits

94f450sd

New member
Apr 21, 2018
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Did you accidentally swap the cam and crank sensor connectors, plugged them into the wrong sensor? That has happened to people before...

This is confusing to say the least.

Checked that too.i don't see how people can mix them up.the crank sensor plug on mine will only reach the crank sensor.

I unbolted the harness holder so I could swap the plugs around to see if that was it,nope.
 

94f450sd

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Apr 21, 2018
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Unfortunately I don't have another truck to take pieces off.i have a couple trucks but they're lb7s.
 

94f450sd

New member
Apr 21, 2018
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What's inside the ficm?I just thought about it and remembered mine has a dent in it from people who worked on it before we got it.
 

94f450sd

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Apr 21, 2018
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Doesn’t the two sensors use different voltage to operate? Sounds like the ecm is junk, but I could be way off

Yes.5v to cam sensor,which I have.12v to the crank sensor,wich I have.my volts are correct.my grounds are good.i had to swap harnesses so I know the block grounds are good.

I have fluctuating voltage on the signal wires.j don't know what those should be but I assume the sensors are working?
 

94f450sd

New member
Apr 21, 2018
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Ok so I been poking wires and connectors while looking at diagrams again.

It appears that I have no power to ign 1 at pin 19 in C1 at the ecm

I powered it up and had someone crank it.it cranked and cranked but no start.i took power away and cranked it myself and it cranked with no start.now I'm back to the 2 second thing.
 

DAVe3283

Heavy & Slow
Sep 3, 2009
3,727
296
83
Boise, ID, USA
The FICM also gets a copy of the crank/cam signals, so if it is damaged, it could be distorting those signals.

If you have a FICM off a running truck, might try swapping it on and see what happens.
 

94f450sd

New member
Apr 21, 2018
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The FICM also gets a copy of the crank/cam signals, so if it is damaged, it could be distorting those signals.

If you have a FICM off a running truck, might try swapping it on and see what happens.

Wish I did but this is the only lly truck I have here.everybody we know has older or newer.a new one is 700.00.
 

94f450sd

New member
Apr 21, 2018
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Ignition 0 pin 18 in c1 at the end is a green wire that goes down to I guess it would be the neutral safety switch on the tranny.i have an extra truck side harness for the truck that I'm using to find out where wires go.

Should I have power to ignition 0 and 1?
 

94f450sd

New member
Apr 21, 2018
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And I have no brake lights.the hydroboost on this has a back up electric pump that should run when you step on brakes without engine running
 

94f450sd

New member
Apr 21, 2018
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Got the brake lights and electric brake backup motor working.

But I still got no fire.think it's time to admit defeat on this one.i hate doing.cars don't win,I'M SUPPOSED TO WIN!!:mad:
 

WVRigrat05

Wound for sound
Jan 1, 2011
3,081
4
38
36
French Creek, West Virginia
If you have the truck in a bind like I did going to the rig one day and are banging from drive to reverse to fast and hit park, the cable pulls on the shifter too hard and won’t let the park switch release, I had to break the on on the LLY unknowing at the time what the hell was going on or what I had broke when I finally got it into gear