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What are the fuse # locations and also are they under the hood or under the dash?
Remove the PCM power relay in the same fuse box and see if the fuse still blows.
Yes, the fuse powers the PCM power relay. If you remove the relay, and the fuse blows or not, we'll know what direction to go.
Ok. Do you have a digital multimeter?
Ok. Look on the side of the relay and the bottom. The pins should be numbered, 30, 87, 87a, 85 and 86.
With the relay out of the fuse box. Check and see what pins in the fuse box for the relay have ground when the key is turned on. There should only be one.
Set the digital multimeter to volts and place the red lead of the meter on the positive post of the battery and the block lead you touch each pin in the relay socket of the fuse box one at a time. You will get battery voltage on the meter reading 12 volts if there is a ground on one of the pins. Do this with the key turned on.
No problem. I'll be on line till 10:30 PM EST. I live on the East Coast.
Remove the fuel pump relay and see if you still have ground on pin #87.
Does it change with the key turned off compared to being on?
You have something grounding out that circuit. Have you had any work done to the vehicle recently and also, what engine does your F150 have?
Check the wiring harness on the passenger side of the engine that goes down to the transmission. We have seen these harnesses contact the exhaust manifold and melt to the metal.
I am going to have to do a little digging through the wiring diagrams. Is it ok to continue this tomorrow evening?
Sounds good. Good night.