Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Coolant temperature sensor
The coolant temperature sensor is bolted onto the housing of the coolant pump.
| Index | Explanation |
|---|---|
| 1 | Coolant temperature sensor |
| 2 | Coolant pump |
| 3 | two-pin plug connection |
| 4 | Characteristic map thermostat |
The coolant-temperature sensor converts the temperature of the coolant into an electrical value (resistance). To do this, a resistance with negative temperature coefficient (NTC) is used. The coolant temperature is one of the measured variables for the following calculations:
- Fuel injection rate
- Nominal idle speed.
A temperature-dependent electrical resistor is used for temperature sensing. The circuit contains a voltage divider where the resistance can be measured depending on the temperature. The resistance is converted into a temperature using a characteristic curve specific to the sensor. An NTC resistor (NTC) is installed in the coolant temperature sensor, whose resistance value drops when the temperature increases.
The resistance changes from 167 kΞ© to 150 Ξ© depending on temperature, which corresponds to a temperature of -40 Β°C to 130 Β°C.
The electrical voltage at the resistor is dependent on the coolant temperature. There is a table stored in the Digital Engine Electronics (DME) that specifies the associated temperature for each voltage value. This compensates for the non-linear relationship between electrical voltage and temperature.
| Index | Explanation |
|---|---|
| 1 | Voltage |
| 2 | Characteristic curve for hot conductor (NTC) |
| 3 | Temperature |
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.