Monitor Description

The ECM detects a malfunction in the coolant heat storage (CHS) system with the CHS tank coolant temperature, the position of the water valve, the running condition of the engine and the operating condition of the soak timer. The soak timer built in the ECM prompts the ECM to actuate the water pump 5 hours after the HV main system has been turned OFF by using the power switch. The ECM then checks the heat retention condition of the CHS tank. In order to ensure the reliable malfunction detection, the ECM detects the CHS tank heat retention malfunction in two ways. Thus, when the following two detection conditions are consecutively met, the ECM determines that the heat retention has deteriorated and sets a DTC.

1. During preheating, the CHS tank outlet water temperature is below 50°C (122°F) (2 trip detection logic).
2. During soaking, the CHS tank outlet temperature is more than 30°C (86°F) lower than that during the got coolant recovery.