P1116

1NZ-FXE ENGINE CONTROL SYSTEM: SFI SYSTEM: P1116: Coolant Temperature Sensor Circuit Stuck for Coolant Heat Storage

DTC P1116 - Coolant Temperature Sensor Circuit Stuck for Coolant Heat Storage

DESCRIPTION

HINT: Although each DTC title says "Coolant Temperature Sensor", these DTCs are related to the coolant heat storage tank outlet temperature sensor.





This system uses an electric pump to supply hot coolant stored in the coolant 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 sensor for the system, which is provided at the tank outlet, is constructed similarly to the engine coolant temperature sensor and is connected to the ECM. The CHS tank outlet temperature sensor has a built in thermistor, whose resistance varies with the coolant temperature.






MONITOR DESCRIPTION

The coolant heat storage (CHS) tank outlet temperature sensor is used for monitoring coolant temperature in the vicinity of the outlet port of the heat storage tank of the CHS system. The resistance of the sensor increases when the CHS tank outlet temperature is low, and conversely, the resistance decreases when the temperature is high. The changes in resistance are reflected in the voltage that is output by the sensor. The ECM monitors the sensor voltage and uses this value to control CHS system properly.
If the sensor output voltage deviates from the normal operating range, the ECM determines that the CHS tank outlet temperature sensor circuit has malfunctioned, and sets a DTC.
Examples:
1) No changes occur in the CHS tank outlet temperature sensor signal (over 1°C [33.8°F]) after a predetermined length of time has elapsed from the start of the coolant recovering.
2) A significant difference (over 25°C [77°F]) exists between the engine coolant temperature signal and the CHS tank outlet temperature sensor signal after a predetermined length of time has elapsed from the start of the coolant recovering.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





WIRING DIAGRAM





INSPECTION PROCEDURE
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.

PROCEDURE

1. CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P1116)
(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 the DTCs.
Result:





HINT: If any other codes besides P1116 are output, perform troubleshooting for those DTCs first.

B -- GO TO DTC CHART
A -- Continue to next step.

2. CHECK COOLING SYSTEM (CHECK FOR CLOGGING IN THE COOLANT SYSTEM)
OK:
Coolant passage has no blockage.
NG -- REPAIR OR REPLACE COOLING SYSTEM
OK -- REPLACE OIL TEMPERATURE SENSOR (CHS TANK OUTLET TEMPERATURE SENSOR)