Engine wiring harness replacement
So. Truck runs rough, injector codes. They are replaced. Still rough, no codes. No solutions. Different mechanic, different computer, still no codes. Changes CPS, as likely culprit?, no improvement. Few days later, after X sits for 4 days( got away fishin'!), wouldnt run. New(third) mechanic finds harness bad in multiple places, non-OEM crimps, frayed n exposed all over... I order brand new in box from Ford harness, confirmed with my VIN. Few days later it arrives. But its different? Has two relays vs one relay and some type of module? Call back dealer, parts, boxes, VIN all match up.... Mechanic puts this harness in, no extra parts, and it runs, not great but better. Throws code PO683? Glow Plug Control Module? Guess thats what my bad harness had, that this new one doesnt. Looking more into it, The Cali versions have GPCM, the others dont?
OK, my VIN is non-Cali, my harness was, now what...??? Please rescue...
https://www.tascaparts.com/oem-parts...y-yc3z12b637ba
Diesel Tech Ron - glow plug video -
Your GPCM could be faulty








