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The lift pump is oscillating about every 1 or 2 seconds. It is a new lift pump. I measured the voltage on the connectors on the fuel pump control module and one of the wires had a voltage that was oscillating with the pump. Another wire was 14volts. This means the voltage oscillating is making the pump oscillate. Is this the computer or could it also be the fuel pump control module? There is enough voltage going to the module. Its just not trigging to use all of it. Could any of the fuel pressure sensors cause this? I replaced the low pressure sensor on HPFP which seems like it could be the only sensor to cause the computer to communicate with the fuel pump since it is all low pressure system?

I ordered a new control module. If I put in the new module and it does the same thing it has to be the computer sending the oscillating voltage to the module?

Does this type of oscillating seem like an electrical component like a capacitor or something? Doesn't seem like a bad ground would oscillate?

maybe I can bypass the computer and send my own voltage to the oscillating wire and see if it still oscillates. Then I know its something in the module causing it to oscillate and not the computer.

Any thoughts on this is helpful. I'm not very familiar with this vehicle yet. And I'm not good at electrical stuff.
 
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