P0116

2AZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0116: Engine Coolant Temperature Circuit Range / Performance Problem

DTC P0116 - Engine Coolant Temperature Circuit Range / Performance Problem

DESCRIPTION

A thermistor is built into the Engine Coolant Temperature (ECT) sensor, of which the resistance value varies according to the ECT.
The structure of the sensor and its connection to the ECM are the same as those of the Intake Air Temperature (IAT) sensor.
HINT: When any of DTCs P0115, P0117 and P0118 are set, the ECM enters fail-safe mode. During fail-safe mode, the ECT is estimated to be 80°C (176°F) by the ECM. Fail-safe mode continues until a pass condition is detected.

HINT: When the DTCs is set, check the ECT by selecting the following menu items on the intelligent tester: DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL / COOLANT TEMP.










MONITOR DESCRIPTION

The ECT sensor is used to monitor the ECT. The ECT sensor has a built-in thermistor with a resistance that varies according to the temperature of the engine coolant. When the ECT becomes low, the resistance of the thermistor increases. When the temperature becomes high, the resistance drops. These variations in the resistance are reflected in the voltage output from the ECT sensor.
The ECM monitors the sensor voltage and uses this value to calculate the ECT. If the sensor voltage output deviates from the normal operating range, the ECM interprets this deviation as a malfunction in the ECT sensor and sets the DTC.
Examples:

- Upon starting the engine, the ECT is between 35°C and 60°C (95°F and 140°F). If the ECT remains within 3°C (5.4°F) of the starting temperature after driving for 250 seconds, the DTC is set (2 trip detection logic).
- Upon starting the engine, the ECT is over 60°C (140°F). If the ECT remains within 1°C (1.8°F) of the starting temperature after driving for 250 seconds, the DTC is set (6 trip detection logic).

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS

ECT sensor cold start monitor:





ECT sensor soak monitor:





TYPICAL MALFUNCTION THRESHOLDS

ECT Sensor cold start monitor:





ECT Sensor soak monitor:





COMPONENT OPERATING RANGE





INSPECTION PROCEDURE
HINT:
- If DTC P0115, P0116, P0117, P0118 and P0125 are output simultaneously, the ECT sensor circuit may be open or shorted. Perform the troubleshooting for DTC P0115, P0117 or P0118 first.
- Read freeze frame data using the intelligent tester. 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 P0116)
(a) Connect the intelligent tester to the DLC3.
(b) Turn the ignition switch to the ON position and turn the tester on.
(c) Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
(d) Read the DTCs.
Result:






B -- GO TO DTC CHART
A -- Continue to next step.
2. INSPECT THERMOSTAT
(a) Remove the thermostat Removal.
(b) Check the valve opening temperature of the thermostat.
Standard temperature:
80 to 84°C (176 to 183°F)
HINT: In addition to the above check, confirm that the valve is completely closed when the temperature is below the standard.
(c) Reinstall the thermostat Installation.
NG -- REPLACE THERMOSTAT
OK -- REPLACE ENGINE COOLANT TEMPERATURE SENSOR