History of truck.. Bought new.. driven into ground.. brought it to me with 200K miles on it and 12 faults.. bank 1 and 2 rich. FPCM code. Fuel pressure out of range. P0121 for dirty throttlebody. several more..

Pull codes, record and clear, clean throttle body, owner had recently had GM dealer fix an airbag code. They suggested a new fuel pump and new O2 sensors.. he replaced these at his house.. New fuel pump sounded really loud.. replaced with new pump.. sounded better.

Pulled FPCM loose to be able to back probe and test fuel pressure circuits.. when I did this it poured water out.. I pulled it apart and let it all dry.. cleaned corrosion from connectors with baking soda / water mixture and tooth brush.. same on connector ( obviously all of this is with the battery undone and the FPCM on a bench ).. Circuits all tested fine.. good ground to sensor, good 5V with key on once the ecm was cleaned and reassembled.. Sensor outputting 3.3xxx volts to FPCM backprobing both the sensor and the ECM.. no drop in voltage.. and yet when I connect my scanner ( the fuel pressure on it read 34psi (225kpag).... I ordered a new sensor from dealer.. replaced (part # has been superseded now).. and it now reads 0 kpag on the scanner..

WTF is going on with this thing.. Im about to just give it back..

The STFT goes as negative as possible as soon as it gets idle set..

 

Fuel pressure code was P0191 with old sensor and with it reading 225kpag...

with new sensor I am getting P0192

 

you poured water out of the FPCM!

I would replace it with a new one, your methods for cleaning the FPCM circuit board makes no sense, especially since you stated there was corrosion as you wont be able to see the actual damage. regardless I would not have reused a water damaged FPCM anyways.

Also checking your wiring harness for corrosion & water, once water gets into a control unit, water gets into the wiring harness & gets pulled through the length of it (this is very common with oil getting into wiring harness from oil sensors/hydraulic camshaft solenoids) its over when the green creep takes hold

get or rent a thermal imager (predator vision) and check the wiring once its hooked back up, you will be able to see hot spots on the thermal imager where there is high resistance in the wire, normally this is a good check without the need to OHM check a circuit and not damaging the wiring insulation.

 

Hey man, if you are at ctc, I have a spare FPCM at my house I could let you try. If it works you can buy it off me.

 

And used fuel pump...and injectors for that matter. LMK