One of the most important sensors in your car is the coolant temperature sensor. This sensor is responsible for telling the computer what the engine coolant temperature is. The computer uses this information to adjust the fuel mixture and ignition timing.
The engine coolant temperature (ECT) sensor is a resistor-based sensor, which measures the temperature of the engine’s coolant. It sends the reading to the car computer (ECU), which adjusts the amount of fuel injection into the combustion chamber.
A coolant temperature sensor wiring diagram is essential for understanding how a car’s engine cooling system works. It can help you troubleshoot issues with the cooling system and avoid costly repairs. The ECT sensor comes in different wiring diagrams and colors depending on the car. In this powerful article, we will explain how to read the 1, 2, and 3-wire coolant temperature sensor wiring diagram.
Coolant Temperature Sensor Wiring Diagram
In this powerful article, we will be more general than specific. Here you will learn a general ECT sensor wiring diagram. For your specific car’s ECT sensor wiring diagram, you should check your car owner’s manual for accurate wire color.
The wiring diagram of the coolant temperature sensor is based on year, make, and model. The color of the engine coolant temperature sensor varies and is color-coded according to the make and model. Below are the 1, 2, and 3 wire engine coolant temperature sensor wiring diagrams.
I . Single Wire Coolant Temperature Sensor Wiring Diagram
A single-wire coolant temperature sensor has only one wire, which goes to the radiator fan relay.
When the temperature of the engine coolant gets hot (almost 98 degree Celsius), the single-wire coolant temperature sensor’s resistance decrease (almost zero) and creates a connection of earth from the engine body.
This earth connection goes radiator’s relay 85 terminals in the fuse box to activate the relay, and the current starts to flow from the fuse box to the radiator fan, which ultimately turns ON the radiator fan.
II. 2 Wire Temp Sensor Coolant Temperature Sensor Wiring Diagram
The Vast majority of ECT sensors are of 2-wire type. In a two-wire coolant temperature sensor, the sensor has two wires.
- 5-volt Reference Wire
- Ground Wire
The sensor gets both of its wires from the ECU.
In a two-wire coolant temperature sensor, the ECU controls the radiator fan through the relay. The sensor does not have a direct connection with the radiator fan. The ECU takes the information from the coolant temperature sensor and decides to turn the fan ON or OFF.
The ECU continuously monitors the temperature of the coolant, when it reaches almost 98 degrees Celsius; the ECU then orders the radiator fan by providing an earth signal to the radiator relay in the fuse box.
When the coolant’s temperature cools down, then the ECU shuts off the radiator fan by cutting the earth signal to the radiator relay in the fuse box.
III. 3 Wire Coolant Temperature Sensor Wiring Diagram
The three-wire coolant temperature sensor is superseded by a two-wire coolant temperature sensor. A three-wire coolant temperature sensor has the following three wires.
- 5 Volt Reference Wire
- Ground Wire
- Earth Signal Wire for Cluster Mounted Temperature Gauge
The two wires, a “5-volt reference”, and a “ground wire” go to the ECU, and the third wire “Earth Signal Wire for Temperature Gauge” goes to the cluster-mounted temperature gauge by providing an earth signal to the temperature gauge.
In three-wire coolant temperature sensors, the ECU does not control the temperature gauge in the cluster. The coolant temperature sensor provides an earth signal according to the temperature of the coolant. Higher the temperature of the engine’s coolant, the lower the resistance of the ECT sensor, and vice versa.
When the temperature of the coolant increases, the resistance of the sensor decreases, which sends high earth signal to the temperature gauge, and you see the temperature gauge indicator fully turned to the hot indication.
Similarly, when the engine coolant temperature decreases, the sensor resistance also decreases, which sends low earth signal to the temperature gauge, and the indicator rests on the cool indication.
The number of wires in a coolant temp sensor varies depending on the specific model and make of the sensor. Generally, most coolant temp sensors have between one and three wires. However, there are some models that have more or fewer wires. The best way to determine the correct number of wires for a particular sensor is to consult the manufacturer’s instructions or specifications.
The coolant temp sensor measures the temperature of the engine coolant and sends the information to the engine control unit. If the sensor is wired backward, it will still work, but the readings will be reversed. For example, if the coolant temperature is actually hot, the sensor will read cold. This is unlikely to cause any damage, but it will give the engine control unit inaccurate information about the engine’s coolant temperature.