The Engine Coolant Temperature(ECT) Sensor measures the temperature of engine coolant. The Engine Coolant Temperature (ECT) Sensor is located near the thermostat housing of the cylinder head. ECT Sensor is a thermistor (A Variable Resistor that Changes Along with ECT) in series with a fixed resistor in the Engine Control Module (PCM). The PCM applies 5 volts to the ECT sensor. The PCM monitors the voltage across the ECT sensor and converts it into a temperature reading. When the engine is cold the ECT sensor resistance is high, and when the engine is warm the ECT sensor resistance is low. Therefore, when the engine is cold the PCM will receive a high voltage input, and when the engine is warm the PCM will receive a low voltage input. The signal from ECT sensor is used for Injection, ignition timing, idle speed and cooling fan control.
The Engine Coolant Temperature High Rationality Diagnostic checks for unusually high engine coolant temperatures under normal operating loads.
PCM monitors difference between the startup and current coolant temperature and compares agaist the threshold while enable condition is met. If the PCM detects that the coolant temperature exceeds the limit under normal operating condition, PCM determines that a fault exists and a DTC is stored.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● This diagnostic introduces a calibratable delay and simultaneously looks out for excessive engine loads. Once the delay period passes and excessive loads have not been experienced, the diagnostic checks whether the undefaulted coolant temperature has exceeded a maximum threshold in order to make a PASS/FAIL determination. | ● Poor connection ● Lack of engine coolant ● Water pump ● ECTS ● PCM |
Enable Conditions | ● Engine Running status ● No disabling faults present ● Coolant Sensor within range ● Undefaulted Coolant Temp ≥ 50°C( 122 °F) ● Undefaulted IAT ≤ 35°C( 95 °F) ● Soak time ≥ 360min or Undefaulted Coolant temp ≤ 45°C( 113 °F) | |
Thresh old value | ● Coolant temperature ≥ 110°C (230 °F) ● Average airflow ＜ 30g/s and filtered airflow ＜ 50g/s | |
Diagnosis Time | ● Continuous More than 12.5 sec.failure for every 15 sec.test) | |
MIL On Condition | ● No MIL ON(DTC only) |
Temp. (°C/°F) | Resistance (kΩ) | Temp. (°C/°F) | Resistance (kΩ) |
-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 |
