Engine Coolant
Temperature Sensor or abbreviated ECT Sensor on vehicle has a function for
measure the temperature of the water cooling of an engine. The Engine Coolant
Temperature Sensor (ECT) is also often referred to as Water Temperature Sensor
(WTS).
The Engine Coolant
Temperature Sensor contains a thermistor and provides the Electronic Control
Unit (ECU) with water cooling temperature reading. The ECU supplies a 5 voltage
reference to the ECT Sensor through a dropping resistor.
When coolent
temperature rises and the ECT sensor becomes hot, ECT sensor serves lower
resistance. When coolent temperature decrease, then the ECT sensor server rises
resistance. This feature is called thermistor type Negative Tempereture
Coefisien (NTC).
The ECU uses signal
from ECT infomation to make the needed calculations for :
- Rich fuel delivery in cold condition
- Knock sensor system
- Avanced ignition in cold condition
- Canister purge solenoid
- Idle RPM control in cold condition
- Cooling fan operation etc.
The ECT sensor has two
terminals, the terminals are THA and E2. For more details note the picture below
:
The Coolant temperature
Meter
The ECU receives the
engine coolant temperature signal from the ECT sensor. As the temperature
increases, the control duty increases
Coolant Temperature
|
Duty
|
Signal (Idle)
|
50
|
16
%
|
4,2
Voltage
|
85
|
48
%
|
2,6
Voltage
|
105
|
48
%
|
2,6
Voltage
|
125
|
79,5
%
|
1,0
Voltage
|
Location
The location of ECT sensor
on engine is below the DCP (SOHC) or below the intake manifold (DOHC). For more
details note the picture below :
Inspection
- Disconnect the ECT sensor connector, turn the ignition switch On and measure the reference voltage (reference voltage value is 4,8 – 5,2 Voltage)
- Connect the ECT sensor connectoe and measure the voltage at the signal terminal according to engine temperature (at the temperature 80 – 900 C is 1,8 – 2,5 Voltage).
- Disconnect the ECT sensor connector and measure the resistance of the ECT sensor.
Coolant Temperature
|
Resistance
|
Coolant Temperature
|
Resistance
|
1200
C
|
99,8
Ω
|
500
C
|
977
Ω
|
1100
C
|
131
Ω
|
400
C
|
1.460
Ω
|
1000
C
|
177
Ω
|
300
C
|
2.238
Ω
|
950
C
|
205
Ω
|
200
C
|
3.510
Ω
|
900
C
|
240
Ω
|
100
C
|
5.672
Ω
|
800
C
|
332
Ω
|
00
C
|
9.425
Ω
|
700
C
|
446
Ω
|
-100
C
|
16.160
Ω
|
600
C
|
670
Ω
|
-200
C
|
28.660
Ω
|
Source : Entry Level
Training General Motor : Engine Management System
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