Faulty 14 Volt Power Module
14 Volt Power Module harness is open or shorted
14 Volt Power Module circuit poor electrical connection
Engine Light ON (or Service Engine Soon Warning Light)
The ECM uses two circuits to control and monitor the state of the 14V power module, often referred to as the accessory DC power control module.
The status circuit functions much like the F Terminal circuit on a generator equipped vehicle. A high side driver in the 14V power module applies a duty cycled voltage to the ECM. The duty cycle indicates 14V power module internal temperature and operational condition. The ECM will detect faults on the 14V power module status circuit when the vehicle is ON.