Have a CAT gp25n forklift, SN AT35A00442. I have a P-04 and F -04 DTC. (No communication between VCM and ECM. also with engine off and key on. Number 2 ignition coil gets extremely hot and smokes
Without being there, and knowing that a coil driver in the ECM is shorted (hot coil, on all the time) and there is no communications with the VCM (comes through the ECM). I would take a WAG that the ECM is toast. But before you replace it thoroughly test the coils and maybe even change them for good insurance. And also make sure the charging voltage is within spec. I am surprised that you didn't mention the ECM fuse blowing, but maybe not. Strange things happen. The electronics are buffered so external sources shouldn't bother them unless it becomes extreme. Such as a jumper misapplied or a Power Probe used wrong.