The Engine Coolant Temperature Sensor (ECTS) is located in the engine coolant passage of the cylinder head for detecting the engine coolant temperature. The ECTS uses a thermistor whose resistance changes with the temperature. The electrical resistance of the ECTS decreases as the temperature increases, and increases as the temperature decreases. The reference 5 V in the PCM is supplied to the ECTS via a resistor in the PCM. That is, the resistor in the PCM and the thermistor in the ECTS are connected in series. When the resistance value of the thermistor in the ECTS changes according to the engine coolant temperature, the output voltage also changes. During cold engine operation the PCM increases the fuel injection duration and controls the ignition timing using the information of engine coolant temperature to avoid engine stalling and improve drivability.
Checking output signals from ECTS every 120 sec. under detecting condition, if an output signal is above 4.9V for more than 4 sec., PCM sets P1115.
Item
Detecting Condition
Possible Cause
DTC Strategy
? This code detects a intermittent open or short to battey in the signal circuit or the sensor
? Poor Connection
? Open or short to battery in signal Circuit
? Open in Ground Circuit.
? Faulty ECTS
? Faulty PCM
Enable Conditions
Case 1
? Engine Running Time > 120sec.
Case 2
? Soak Time > 360min.
? Engine Running
Threshold value
? Coolant signal > 4.9V
Diagnosis Time
? Continuous (More than 4 sec. failure for every 120 sec. test)
MIL On Condition
? DTC only (NO MIL ON)
Temp. (°C/°F)
Resistance (k?)
-40(-40)
48.14
40(104)
1.15
-20(-4)
14.13 ~ 16.83
60(140)
0.59
0(32)
5.79
80(176)
0.32
20(68)
2.31 ~ 2.59