am having a heck of a time diagnosing my 03 e350 with a 7.3 powerstroke engine. It started throwing IDM codes so I ohm texted the harness and nothing was in spec. So I replaced both harness’ and I also replaced the glow plugs while I was in there. Now I’m getting all these codes in the picture, including most of the passenger side glow plug circuit. I’m having runability issues. It starts and idles fine, but it’ll get stuck at certain speeds while driving, and won’t accelerate above them. It’ll also sometimes start decelerating.

Any thoughts on what I should be checking/testing? I don’t want to spend an insane amount of money fixing it up if I don’t have to. It’s a grooming van and we have a new one that’s being converted. I just need this one to run reliably for a few more months. (Probably why she’s breaking down, she knows she’s being replaced &#128514

I changed the fuel filter a few weeks ago and just changed the oil pressure sensor as well.

 

Welcome to the FTE!

Have you cleared codes after changing harnesses?
Have you done BUZZ test?

​​​​​If in tank pickup showerhead has detoriated,fuel pump will suck air below 1/4 tank.

 

I have done a Buzz test: it shows 6, 8 and 1 are all high to low side open. I did not clear the codes after changing the harness, I wasn’t sure if I should or if they would’ve just gone away if the problem was fixed lol

 

Check battery connections, cables and voltages. Reference different points for your ground prbe to see if there is a bad engine ground.

Where you are measuring from might by why the harness readings were out.

 

Go ahead and clear the codes, now that you've documented them and have changed the UVC harnesses. Let's see what comes back after a short drive where you reproduce the symptoms.

If 6, 8 and 1 are still coming up on the buzz test (P1316, then P1271, P1276, P1278), I'd recommend measuring resistance from injector power to injector ground for these three injectors. If they measure open, the harness you installed is suspect. If that reads good, you can check the same injectors at the 42 pin connector. If good there, go to the IDM connector and check at that connector. See if you can find the open circuit. I think high to low open is a measurement of the injector common (high) to the injector control pin (low), essentially a measurement of the resistance across the injector solenoid and associated wiring.

What brand are the harnesses you purchased?

 

X2 on what harnesses were purchased and from where. That could well be the root of your current troubles. Still have the old harnesses? Might try swapping new for old or even one side to the other and see if problems follow. Oh and the glow plugs can be a real bad day if not factory replacements, beru I think is the brand, and from a trusted source. Here's what can happen using other than the good stuff. I swapped these out for a friend and almost didn't get 2 of them out, and they looked like new Autolite's.