P1121
1NZ-FXE ENGINE CONTROL SYSTEM: SFI SYSTEM: P1121: Coolant Flow Control Valve Position Sensor Circuit Stuck
DTC P1121 - Coolant Flow Control Valve Position Sensor Circuit Stuck
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
The ECM monitors the position of the water valve based on the valve position signal that is output by the water valve position sensor (potentiometer), which is coupled coaxially to the valve. The water valve effects control in three steps as indicated above, and the ECM determines the position of the valve according to the voltage of the respective step.
In order to ensure the proper monitoring of the water valve, the ECM checks for malfunctions with the combination of the output of the potentiometer and CHS tank outlet temperature sensor.
If no changes occur in the valve position signal that is being input into the ECM or if the response signal from the water valve is very slow, despite the ECM commanding the water valve motor to operate the ECM determines that a malfunction has occurred in the water valve position sensor circuit, and sets a DTC.
MONITOR STRATEGY
Potentiometer detection
Tank outlet coolant temperature detection
TYPICAL ENABLING CONDITIONS
Potentiometer detection
Tank outlet coolant temperature detection
TYPICAL MALFUNCTION THRESHOLDS
Potentiometer detection
Tank outlet coolant temperature detection
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
- Although each DTC title says "Coolant Flow Control Valve", these DTCs are related to the water valve.
- CHS stands for Coolant Heat Storage.
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:
- If DTCs P1121 and P1150 are detected simultaneously, there may be malfunction in the water valve system.
- If DTC P1121 is detected, coolant passages may be clogged.
- 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 OTHER DTC OUTPUT (IN ADDITION TO DTC P1121)
(a) Connect Techstream to the DLC3.
(b) Turn the power switch ON (IG).
(c) Turn the tester ON.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Code.
(e) Read DTCs.
Result:
HINT: If any other codes besides P1121 are output, perform troubleshooting for those DTCs first.
B -- GO TO DTC CHART
A -- Continue to next step.
2. PERFORM ACTIVE TEST USING TECHSTREAM
(a) Connect Techstream to the DLC3.
(b) Turn the power switch ON (IG).
(c) Turn the tester ON.
(d) Put the engine in inspection mode Service Precautions.
(e) Start the engine and warm it up.
(f) Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the Water Flow Valve 3, Activate the Water Flow Valve 4 or Activate the Water Flow Valve 5.
(g) Measure the voltage between terminals WBAD and E2 of the ECM connector.
Standard voltage:
NG -- REPLACE WATER W/BRACKET VALVE ASSEMBLY
OK -- Continue to next step.
3. CHECK COOLING SYSTEM (CHECK FOR CLOGGING IN THE COOLANT SYSTEM)
OK:
Coolant passages are not clogged.
NG -- REPAIR OR REPLACE COOLING SYSTEM
OK -- REPLACE ECM