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Discussion Starter · #1 ·
hey guys, new here posting, i also have a post in another topic, but am hoping to get some help, i have been banging my head against the wall and am totally out of options. I have got a lot of help from these sites working on my truck.... so my problem started with my truck dying on me in the morning, started it back up and it ran for 5 min until it died again. after that the relay behind the radio quit clicking which is the*fuel*pump*relay. so I have no power to the fuel pump. since then I have been doing test after test. I have checked all fuses under the hood and in the cab. all are good. swapped relays around, tested the computer plug for all grounds and positives and all passed. I have manually grounded the fuel pump control wire from the pcm, and the fuel pump relay clicks and pump will run. I have also done the same on the gp relay circuit and the IDM circuit, and everything acts as it should. The problem I am having is the computer will not send the ground control to any of these circuits. Not with the old computer or the new one. I have also tested power at the ignition switch and the OBDII port. All is good. The OBDII port has the constant 12v+ and the grounds. I have also striped the wire looms around the pcm, IDM, and the 3 big plugs going into the firewall looking for bad wires. Took all the plugs out and inspected them including the 42 pin plug above the drives valve cover. All pins were clean. I have done basically every test I can think of. so I purchased a new*pcm, installed it withbatteries*disconnected of course. and nothing. very upset and almost want to take it to the dealer, but I cant. I'm a long time mechanic and this is just really getting to me.*fuel*bowl*heater*and fuse is fine by the way. please help....
 

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Check the fuel pump inertia switch behind the passenger kick panel
 

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Discussion Starter · #3 ·
That's good as well. If I manually ground the circuit at the pcm plug, the pump will run. I just can't get either the new computer or the old one to send the control command to multiple sources

sent from jsbelectro
 

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Have you confirmed that power is getting to the PCM connector to power it up? Sounds like something is wrong on one of the circuits that powers the PCM (there are at least 3 of them). I don't have access to the pinout to point you to which pins should be hot, but could get that for you later this evening.
 

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Discussion Starter · #6 ·
I have downloaded all the wire schematics for the pcm connector, the 42 pin connector, obd connector etc. I have tested all the grounds, the one constant 12+ and the 3 grounds. All tested good. I am kinda stumped though on a couple things. With the key off when I go to check some of the computer controlled ground circuits at the pcm plug like glow plug, fuel pump relay, and wait to start light, I get about 11volts+. But when I manually ground those circuits, they will work as they should. Is it because when I'm using my dvom on a grounding circuit, is it completing a ground or completing a circuit, or am I reading some residual back voltage from the coils in the relay associated with that ground. The second stumper is when I manually ground one of the ground control circuits is that there is no arcing or sparking indicating a ground line has a short to +. I have taken the under the hood fuse/relay box out and inspected it, and it seems good. That is without completely tearing it apart. Haven't dissassembeled the cab fuse box.

sent from jsbelectro
 

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Discussion Starter · #7 ·
Forgot to say that there are 3 grounds and 3 positives to the pcm, all were ok. That was one thing I wanted to make sure of. Also I can't communicate with pcm using torque. I know it works on ford's because I used it on a 07 taurus.

sent from jsbelectro
 

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Discussion Starter · #8 ·
Well I checked every fuse box and all was goid. Went back to basics and checked all my grounds and hots to the computer, checked the relays, fuses, ignition wires, took all the big plugs apart, pulled wire looms looking for corrosion or a short to ground/power, and went to my refrence line that was supposed to be 5 volts, and I barely had 1 volt. Started unplugging sensors on that 5 volt refrence line, and got to the EBPV sensor, and everything came to life. Truck starts and runs. Just need to replace that sensor now. What's bizarre is that having that sensor short to ground actually caused everything to point to a bad pcm. I want to thank everyone for all your help and I will stick around to help any of you when you need it.

sent from jsbelectro
 

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I've heard of the ebp sensor doing that one other time. It's so rare I never thought of it.
 

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That 5v line can be tricky. Glad you found it and hope all the hair you pulled out regrows!
 

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GREAT info to keep in the memory banks. Thanks for sharing.
 
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