Monitor Description

To check the heat retention of the tank in the coolant heat storage (CHS) system, the ECM may cause the water pump of the CHS system to operate 5 hours after the power switch has been turned OFF.

A timer and a clock are contained in the ECM internal circuit, and the timer starts when the power switch is turned OFF (this process is called the "soak mode").

When the HV main system is started by the power switch, the ECM monitors its internal circuit. If the ECM detects a deviation between the clock and the timer, or an abnormal condition during a comparison between the starting history and the length of time the HV main power has been turned OFF, the ECM determines that its internal circuit has a malfunction and sets a DTC.