DSG-423 ENGINE CONTROLS
08-5
Engine Coolant Temperature (ECT) Sensor
The Engine Coolant Temperature (ECT) Sensor is a
thermistor (a resistor which changes value based on
temperature) mounted in the engine coolant stream.
Low coolant temperature produces a high resistance of
100,000 ohms at -40°C (-40°F). High temperature
causes a low resistance of 70 ohms at 130°C (266°F).
The GCP supplies a 5 volt signal to the ECT sensor
through resistors in the GCP and measures the voltage.
The signal voltage will be high when the engine is cold
and low when the engine is hot. By measuring the
voltage, the GCP calculates the engine coolant
temperature. Engine coolant temperature affects most
of the systems that the GCP controls.
After engine start-up, the temperature should rise
steadily to about 85°C (185°F). It then stabilizes when
the thermostat opens. If the engine has not been run for
several hours (overnight), the engine coolant
temperature and intake air temperature displays should
be close to each other. A fault in the engine coolant
sensor circuit will set a DTC 221 or DTC 222.
TEMP. C° TEMP. F°
NOM Rt,
(OHMS)
NOM E
OUT
(VOLTS)
-40 -40 925,021 4.54
-35 -31 673,787 4.50
-30 -22 496,051 4.46
-25 -13 368,896 4.41
-20 -4 276,959 4.34
-15 5 209,816 4.25
-10 14 160,313 4.15
-5 23 123,485 4.02
0 32 95,851 3.88
5 41 74,914 3.71
10 50 58,987 3.52
15 59 46,774 3.32
20 68 37,340 3.09
25 77 30,000 2.86
30 86 24,253 2.62
35 95 19,716 2.39
40 104 16,113 2.15
45 113 13,236 1.93
50 122 10,926 1.72
55 131 9,061 1.52
60 140 7,548 1.34
65 149 6,332 1.18
70 158 5,335 1.04
75 167 4,515 .91
80 176 3,837 .79
85 185 3,274 .70
90 194 2,804 .61
95 203 2,411 .53
100 212 2,080 .47
105 221 1,801 .41
110 230 1,564 .36
115 239 1,363 .32
120 248 1,191 .28
125 257 1,044 .25
130 266 918 .22
135 275 809 .19
140 284 715 .17
145 293 633 .15
150 302 563 .14
Voltage values calculated for VREF = 5 volts (may vary ± 15% due
to sensor and VREF variations)
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