P1122

1NZ-FXE ENGINE CONTROL SYSTEM: SFI SYSTEM: P1120: Coolant Flow Control Valve Position Sensor Circuit

DTC P1120 - Coolant Flow Control Valve Position Sensor Circuit

DTC P1122 - Coolant Flow Control Valve Position Sensor Circuit Low

DTC P1123 - Coolant Flow Control Valve Position Sensor Circuit High

DESCRIPTION





This system uses an electric pump to supply hot coolant stored in the heat storage tank into the cylinder head of the engine, in order to optimize engine starting combustion and reduce the amount of unburned gas that is discharged while the engine is started. Before the engine starts, the ECM operates the electric water pump to direct the hot coolant in the heat storage tank into the engine, in order to heat the cylinder head (this process is called "preheat mode"). The duration of the operation of the electric water pump is variable, depending on the temperature of the cylinder head. During the normal operation of the engine, the water valve opens the passage between the cylinder head and the heater and closes the passage between the cylinder head and the tank. During preheat mode in which the cylinder head is heated, the water valve opens the passage between the tank and the cylinder head, in order to allow the coolant to flow from the tank to the cylinder head. At this time, in order to warm up the intake port quickly before the engine is started, the coolant flows in the reverse direction.
The water valve for the coolant heat storage (CHS) system, which is located at the heater hoses, controls the coolant passages to the engine, heater core, and the CHS tank in accordance with the operating conditions of the system.
The water valve consists of a water valve, valve position sensor, and valve control motor. The potentiometer, which is coupled coaxially to the water valve, converts the valve position into voltage and transmits it to the ECM in the form of a position signal.






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





MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS

P1120:





P1122:





P1123:





COMPONENT OPERATING RANGE





WIRING DIAGRAM





INSPECTION PROCEDURE
HINT: Although each DTC title says "Coolant Flow Control Valve", these DTCs are related to the water valve.
CAUTION: Be careful when replacing any part in the system or changing the coolant because the coolant in the heat storage tank is hot even if the engine is cold.
HINT:
- To check 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.
- Read freeze frame data using Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air/fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction Freeze Frame Data.

PROCEDURE

1. CHECK ECM (WBAD - E2 VOLTAGE)




(a) Turn the power switch ON (IG).
(b) Measure the voltage between the terminals WBAD and E2 of the E4 and E7 ECM connectors.
Standard voltage:





HINT: After the HV main system is turned OFF (READY to IG OFF condition), the valve position will be set to position A.

OK -- CHECK FOR INTERMITTENT PROBLEMS
NG -- Continue to next step.

2. INSPECT WATER M/BRACKET VALVE ASSEMBLY




(a) Disconnect the W5 water valve connector.
(b) Measure the resistance between terminals WSL1 and WSL2 of the water valve connector.
(c) Measure the resistance between terminals WSAD and E2 of the water valve connector.
Standard resistance:





(d) Reconnect the water valve connector.
NG -- REPLACE WATER W/BRACKET VALVE ASSEMBLY
OK -- Continue to next step.

3. CHECK HARNESS AND CONNECTOR (WATER VALVE - ECM)




(a) Disconnect the W5 water valve connector.




(b) Disconnect the E4 and E7 ECM connectors.
(c) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):






Standard resistance (Check for short):





(d) Reconnect the water valve connector.
(e) Reconnect the ECM connectors.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ECM