Power Down Sequence

The Inverter System Controller (ISC) must conduct a normal power down sequence. Whenever the ignition is turned to the OFF or ACC position, modules powered up by the ISP-R circuit immediately shut down. However the ECM, Inverter System Controller (ISC), and the BECM stay on, until the power down sequence is complete. The ECM and Inverter System Controller (ISC) stay powered by controlling their own dedicated power relays. The BECM is powered directly from the low voltage battery which permits wake-up function when the vehicle is off. During the power down sequence the Inverter System Controller (ISC):

• requests the ECM to cut power to the injectors and ignition coils (engine shut down)
• disables the high voltage inverters
• requests the BECM to disable the DCDC converter
• requests the BECM to open the high voltage contactors
• discharges the high voltage inverter capacitors
• opens the Inverter System Controller (ISC) power relay

If the power down sequence does not execute correctly, it is considered an abnormal shut down which may result in the ECM, the Inverter System Controller (ISC) and the BECM storing DTCs.