Power Control Relay

THE SOLE PURPOSE OF THE POWER CONTROL RELAY IS TO SEPARATE THE MAIN BATTERY AND AUXILIARY BATTERY DURING THE BRIEF PERIOD OF INITIAL STARTER IN-RUSH (APPROXIMATELY 20-40MS DURATION). THIS OCCURS DURING THE INITIAL ENGAGEMENT OF THE STARTER MOTOR. THE RELAY IS NORMALLY CLOSED, ALLOWING CONNECTION BETWEEN THE BATTERIES WHEN DE-ENERGIZED (OFF). ONE SIDE OF THE RELAY COIL IS DIRECTLY CONNECTED TO CHASSIS GROUND. THE RELAY IS ENERGIZED WHEN 12.0 VOLTS IS SUPPLIED ON THE CONTROL CIRCUIT TO THE OTHER SIDE OF THE COIL. THE PCM INDIRECTLY  CONTROLS THE POWER SUPPLY TO ENERGIZE THE POWER CONTROL RELAY BY TURNING ON THE PCR CONTROL RELAY INSIDE THE POWER DISTRIBUTION CENTER (PDC). THE PCR CONTROL RELAY IS TYPICALLY A PRINTED CIRCUIT BOARD (PCB) RELAY THAT IS CONTROLLED USING A LOW SIDE DRIVER (LSD) CONTROL INSIDE THE PCM.