P0090 help!

On the way home from Antrim last month, after just filling up at the station by the track, my truck started getting the loud injector rattle that comes along with the rail pressure being to high from a bad or disconnected fpr. Shortly after the truck went into reduced power mode and a P0090 code came up. Assuming it was a bad fpr I got the truck home, replaced the fpr, and no difference. Any ideas? Need to get it going soon, the girlfriends ss cobalt sucks for a construction vehicle and sucks even worse in the snow..

That's a circuit code for the regulator. Zero voltage to the regulator will max it out, check the wiring/circuit to the regulator.

With a voltmeter and the key on which pins on the fpr should have voltage and ground? And what voltage? Also why is there a 3 pin harness on one side of the fpr pigtail and the fpr side of it only has 2?

Shook the wires on the pigtail it straightened up for a couple seconds. That's definitely where it's coming from. Just not sure if its at the fpr, the harness side of the pigtail, or the harness itself..