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I encountered a Cold No Start problem last fall with my 2003 PSD CCLB. It is a California truck and I was in WY when the night temperatures were dipping close to freezing. The next morning the 7.3 refused to start although there was a little whitish smoke from the exhaust. A good ol' boy from TN in the adjoining campground heard it cranking and came over. He suggested that my Cali truck didn't like the cold weather (I didn't either!) and that he had no problem with his Dodge that had been plugged in overnight. I searched and found the cord to the block heater, knowing that I had never used it before and doubted that the original owner had used it either. A half hour later the truck reluctantly stumbled to life and from then on I plugged it in whenever I expected the temps to be below 40 at night and did not have a problem.
When I got home I checked for codes and the only one was P0380. I then pulled the connectors off from the GPCM and checked the contacts, finding all to be tight. I then measured the resistance of each GP from the connectors and all were okay. I took my ammeter and with the plus lead on the battery probed each GP individually and each one displayed >10 Amps. Thinking that this 'proved' the GPCM was bad, I ordered a new one for ~$100 and waited for it.
After installing the new GPCM, I had the same P0380 code! See the most recent pic of the code display on my laptop. It appears that there is no serial communication on the lines between the GPCM and the ECU. Has anyone else encountered this failure? The communication lines traverse two connectors and I am thinking that I could cut these data lines and hard wire from the connectors on the GPCM to the connector of the ECU, thereby bypassing the intermediate connectors. Does anyone know what the voltage levels of these data lines should be or how to diagnose a problem?

Thanks for any help!
PTC on 12152019.JPG
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