PCM = Power Control Module also known as ECM (Engine Control Module ) meaning the engine computer. It is located under right side of dash.
The ECM would be less likely to be the cause as they seldom shorts out.
Which engine variant do you have, 5.7 or 7.4 L?
The fuel pump circuit would be more likely to be the cause. As the wires runs from fron to rear of vehicle, there could be a possibility of some wires being damaged to external elements such as abrasion or rodent damages. Intermittent shorting is never easy to detect and a stroke of luck helps.
Fuel pump relay is located on right side of firewall in relay box.
I could not find any detailed diagrams and description of the relay box or other components.
Unplug the fuel pump relay.
Use a 10 A fused wire apply battery voltage to terminal B.
Alternatively you can use the fuel pump test connector locatred near relay box to connect the wire.
If fuse blows, you have a short in the fuel pump circuit.
Another components wiring that could cause the shorting of the fuse would be the fuel pump oil pressure switch, located at left rear of engine for 5.7L and at front side of engine block near oil pan for 7.4L.
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Wednesday, October 11th, 2017 AT 10:18 AM