ON-VEHICLE SERVICE
Engine Coolant Temperature (ECT) Sensor
Description
The Engine Coolant Temperature (ECT) sensor threads into the coolant outlet connector. The ECT is a negative
thermal coefficient sensor.
Operation
The ECT provides an input to the Engine Control Module (ECM). As temperature increases, resistance of the sensor
decreases. As coolant temperature varies, the ECT sensor resistance changes resulting in a different voltage value
at the ECT sensor signal circuit. The ECM uses the input to control air-fuel mixture, timing, A/C compressor and
radiator fan on/off times.
Removal & Installation
1. Disconnect the negative battery cable.
2. Drain the cooling system (See Cooling System Draining Procedure in Section 06 Cooling System).
WARNING!
Never remove the pressure relief cap under any conditions while the engine is operating or hot. Failure to follow
these instructions could result in personal injury or damage to the cooling system or engine. To avoid having
scalding hot coolant or steam blow out of the cooling system, use extreme care when removing the pressure
relief cap. Wait until the engine has cooled, then wrap a thick cloth around the pressure relief cap and turn it
slowly one turn (counterclockwise). Step back while the pressure is released from the cooling system. When you
are certain all the pressure has been released, (with a cloth) turn and remove the pressure relief cap. Failure to
follow these instructions may result in serious personal injury.
3. Disconnect the coolant temperature sensor electri-
cal connector.
CAUTION:
Remove the coolant temperature sensor when
the engine is cold.
4. Remove the engine coolant temperature sensor
(1).
(Tighten: Engine coolant temperature sensor to 20
N·m)
5. Discard the O-ring.
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