Monitor Description
WARNING: This page is about a different car, the 2004 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.
The HV control ECU performs diagnostic monitoring to verify proper operation of vehicle systems. One of these monitors checks the inside of the HV control ECU for a bad integrated circuit which actuates a relay. If the HV control ECU detects malfunction, it will illuminate the MIL and set a DTC.