The engine coolant temperature sensor is located next to the engine coolant temperature switch on the engine coolant bridge (under the air intake plenum), engine coolant temperature, to the Powertrain Control Module (PCM). Diagnosis is accomplished through the code output of the PCM.4.5L, 4.6L, and 4.9L Engines
The coolant temperature 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 (100,000 ohms at -40°F -40°C), while high temperature causes low resistance (70 ohms at 266°F/ 130°C).
The PCM supplies a 5 volt signal to the ECT sensor through a resistor in the PCM and monitors the terminal voltage. Since this forms a series circuit to ground through the ECT sensor, high sensor resistance (low temperature) will result in high PCM terminal voltage. When the ECT sensors resistance is low (high temperature), the terminal voltage will be drawn lower. This terminal voltage indicates engine coolant temperature to the PCM.
REMOVAL & INSTALLATION
- Disconnect the negative battery cable.
- Remove the air intake plenum and the intake manifold.
- Remove the electrical connectors from the engine coolant temperature sender, and the engine coolant temperature sensor.
- Remove the throttle body and heater inlet hoses from the bridge.
- Remove the engine coolant temperature sender, and the engine coolant temperature sensor.
- Remove the throttle body inlet hose fitting, if necessary.
- Remove the engine coolant bridge bolts and the upper seals. Remove the engine coolant bridge and the lower seals.
- Install the engine coolant bridge, the bolts and seals.
- Slide the upper seals onto the bolts, insert the bolts into the engine coolant bridge, and slide the lower seals onto the bolts. Tighten the bolts to 22 ft. lbs. (30 Nm).
- Install the engine coolant bridge fitting. Tighten the fitting until fully seated and not stripped.
- Install the engine coolant temperature sensor and seal. Tighten to 18 ft. lbs. (25 Nm).
- Install the engine coolant temperature sender and tighten the sender to 15 ft. lbs. (20 Nm).
- Attach the throttle body and heater inlet hoses to the bridge.
- Reattach the electrical connectors.
- Install the intake manifold and air intake plenum.
- Connect the negative battery cable.
- Properly relieve the cooling system pressure.
- Make sure ignition is in the OFF position.
- Detach the electrical connector to the coolant temperature sensor.
- Remove sensor carefully.
- Coat threads of sensor with proper type sealant.
- Install sensor to engine and tighten to 15 ft. lbs. (20 Nm).