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Did you install your new engine harness yourself, or did you have it done?
Did the engine EVER run with that new harness installed? From the way I read the thread, the answer is probably "no".
Is connector C1282 connected (this is the mid harness connector I mentioned earlier)? I would like to see you post a picture of it. It is a square, 12 wire, connector (tan color).
Even though load testing of circuits is best, you seem to be looking at a complete open circuit somewhere (based on your description of findings), so simple continuity testing may help, but you may have to do it at various positions along the harness.
That said, answers to the questions below MIGHT help you to narrow down the general location of the issue. SO - please ALSO provide the answers to the questions below (WITH the ignition switch in the start/run position, ie with keyed power "on"):
.
Is there power at both sides of fuse 22 (check both sides of the fuse with your DVOM)?
Is there power at the MAF sensor on that red wire (AGAIN - "Key On")?
Is there power at the fan clutch on that red wire?
Is there power at the GPCM, pin 9, on that wire?
Is there power to that wire at Connector C1282 (pin 10)? You can back probe that wire without disconnecting C1282, check both sides.
Do all other appropriate accessories power up with the key on (specifically the instrument cluster)?
Trying to help you narrow down the location of the issue by asking the questions above. You may have to open up that new harness looking for the issue, or ultimately you may have to buy another harness.
I installed the harness mysef,the truck has never ran with the new harness. i checked connector c1282, the red wire at the plug had a bad connection and i fixed it and now i got the red wire to have consistent 12v at every sensor. f22 has 12v at both sides. the instrument cluster works fine. I was cranking it today and i have good icp pressure. it wants to fire up and blows a bunch of black smoke. i have good ficm volts, good ficm sync. i noticed when ever it builds plenty of oil pressure there’s a weird electrical clicking sound but i cant locate it. It is supper close to firing up
Here are the codes i have coming up, im not worried about most of them because i have most of the parts disconnected. im mainly just trying to get it to fire up and run, ill fix the little codes later. im more concerned about the important codes with the pcm and computers. i have the intake manafold off, would that effect how it runs?
The 6.0L has a feedback circuit on the fuel pump supply power. This is simply a circuit spliced into the voltage feed to the fuel pump. The splice is usually located close to the PCM. The PCM monitors this feedback circuit to ensure that there is proper voltage being sent to the fuel pump. As it activates the fuel pump relay, it expects to see battery voltage on the feedback circuit. If it sees voltage that is too low or no voltage at all, it may set P0231.
Possible causes: Open/short circuit, relay, inertia switch or fuel pump / fuel pump fuse (DTC is for no voltage on the fuel pump monitor circuit)
btw - this fuel pump relay is not serviceable separately - it can be serviced only with a replacement of the Central Junction Box, CJB, under the steering column (or by having a company that repairs circuit boards do the replacement).
Also, I was hoping to see a pic of C1282 ................