Monitor Description
A potentiometer is provided in the coolant heat storage (CHS) system. The ECM uses the valve position signal output by the water valve for effecting control that is appropriate for the operating condition of the engine. The water valve effects control in three steps as indicated below, and the ECM determines the position of the valve according to the voltage of the respective step.
If the signal output by the water valve exceeds the normal range, the ECM determines that a malfunction has occurred in the water valve position sensor circuit and outputs a DTC.
Water Valve Operation
WATER VALVE OPERATION CHART
| System Condition | Valve Position | Coolant Flow |
|---|---|---|
| Normal engine operation | C | Engine to Cabin heater |
| Preheat mode | A | Coolant heat storage tank to Engine |
| Coolant recovering (after engine stop) | A | Engine to Coolant heat storage tank |
| Coolant recovering (while engine is running) | B | Engine to Cabin heater and Coolant heat storage tank |
| Soak mode | A | Coolant heat storage tank to Engine |