Vehicle Power (VPWR)
WARNING: This page does not describe the selected car, but rather 9 other vehicles, including the 2018 Ford Transit-350 HD, 2018 Ford Transit-350, 2018 Ford Transit-250, 2018 Ford Transit-150, and 2018 Ford F-550 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
The VPWR is the primary source of PCM power. The VPWR is switched through the PCM power relay and is controlled by the PCM. With the ignition in the START or RUN position, voltage is supplied to the PCM through the ISP-R circuit. When the PCM senses that the ignition is in the START or RUN position, the PCM grounds the PCMRC circuit to energize the relay and close the internal contacts. With the relay contacts closed, VPWR is supplied to the PCM.