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SEF594K
Component Description
NHEC0069
The engine coolant temperature sensor is used to detect the
engine coolant temperature. The sensor modifies a voltage signal
from the ECM. The modified signal returns to the ECM as the
engine coolant temperature input. The sensor uses a thermistor
which is sensitive to the change in temperature. The electrical
resistance of the thermistor decreases as temperature increases.
SEF012P
<Reference data>
Engine coolant
temperature °C (°F)
Voltage* V Resistance kΩ
−10 (14) 4.4 7.0 - 11.4
20 (68) 3.5 2.1 - 2.9
50 (122) 2.2 0.68 - 1.00
90 (194) 0.9 0.236 - 0.260
*: These data are reference values and are measured between ECM terminal 70
(Engine coolant temperature sensor) and body ground.
CAUTION:
Do not use ECM ground terminals when measuring input/
output voltage. Doing so may result in damage to the ECM’s
transistor. Use a ground other than ECM terminals, such as
the ground.
On Board Diagnosis Logic
NHEC0070
Malfunction is detected when an excessively high or low voltage
from the sensor is sent to ECM.
FAIL-SAFE MODE
NHEC0070S02
When this malfunction is detected, the ECM enters fail-safe mode
and the MIL lights up.
Detected items Engine operating condition in fail-safe mode
Engine coolant tem-
perature sensor circuit
Engine coolant temperature will be determined by ECM based on the time after turning ignition switch
“ON” or “START”.
CONSULT-II displays the engine coolant temperature decided by ECM.
Condition
Engine coolant temperature decided (CONSULT-II
display)
Just as ignition switch is turned ON or Start 40°C (104°F)
More than approx. 4 minutes after ignition ON or
Start
80°C (176°F)
Except as shown above
40 - 80°C (104 - 176°F)
(Depends on the time)
GI
MA
EM
LC
FE
AT
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
DTC P0115 ENGINE COOLANT TEMPERATURE SENSOR (ECTS) (CIRCUIT)
Component Description
EC-171
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