What does a coolant temperature sensor do
The Coolant Temperature Sensor is an important component in the engine cooling system. Its main function is to measure the temperature of the engine coolant and transmit this data to the Engine Control Unit (ECU) or Electronic Control Module (ECM). Based on this temperature data, the ECU can make appropriate adjustments to ensure the engine operates at its optimal working condition.
The Coolant Temperature Sensor typically consists of a thermistor, which is a temperature-sensitive resistor. The resistance value of the thermistor changes with temperature. In the Coolant Temperature Sensor, the thermistor is exposed to the coolant, and its resistance value varies accordingly as the coolant temperature changes.
The location of the Coolant Temperature Sensor can vary depending on the vehicle model, but it is usually installed near the coolant passage in the engine cooling system, such as the cylinder head or coolant pipes. It is connected to the vehicle's electronic system through an electrical connection.
Coolant Temperature Sensor Circuit
How Does coolant temperature sensor Work?
The engine coolant temperature sensor has a slender head that comes into contact with the coolant. It contains a negative temperature coefficient thermistor. As the engine coolant temperature gradually increases, the resistance value of the thermistor decreases, and vice versa. Therefore, when the engine coolant temperature changes, the output voltage of the sensor also changes. Upon receiving the signal from the coolant temperature sensor, the ECU makes adjustments to the fuel injection timing and ignition timing of the engine.
The working principle of the engine coolant temperature sensor
Symptoms of a bad coolant temperature sensor
What happens when coolant temperature sensor goes bad? When the engine coolant temperature sensor is damaged, the car may experience a series of symptoms. Here are some common malfunctions:
- Inaccurate or non-functional temperature gauge: This can lead to uncontrolled engine temperatures.
- Fuel injection system failure: The engine may not accurately calculate the required fuel injection amount.
- Engine shaking or black smoke emission: The engine may not accurately calculate the theoretical idle speed, resulting in unstable idle.
- Increased fuel consumption and decreased power: The engine's performance and fuel efficiency will be affected.
- Fan not turning or constantly running: When the engine coolant temperature sensor experiences an open or short circuit fault, the electronic fan may run at high speed.
If any of the above symptoms are observed in the vehicle, it is likely that the issue is caused by a faulty coolant temperature sensor. These phenomena can potentially damage the engine's lifespan, so it is important to promptly visit an automotive repair shop for maintenance.
What causes a coolant temperature sensor to go bad
There are several factors that can contribute to the failure of a coolant temperature sensor:
- Wear and tear: Over time, the coolant temperature sensor can experience normal wear and tear, which can lead to its deterioration and eventual failure.
- Electrical issues: Problems with the electrical connections, such as corrosion or loose connections, can interfere with the proper functioning of the coolant temperature sensor.
- Contaminants in the coolant: If the coolant used in the engine is contaminated with debris, rust, or other substances, it can cause damage to the coolant temperature sensor and lead to its failure.
- Exposure to extreme temperatures: Coolant temperature sensors are exposed to high temperatures in the engine compartment. Continuous exposure to extreme heat or rapid temperature changes can cause the sensor to malfunction or fail.
- Fluid leaks: Coolant leaks or other fluid leaks near the coolant temperature sensor can expose it to moisture or other corrosive substances, leading to sensor failure.
- Manufacturing defects: In some cases, a coolant temperature sensor may have manufacturing defects or quality issues that can cause premature failure.
Common coolant temperature sensor error codes
P0018: Coolant Temperature Sensor Circuit High Input. (Possible causes: Sensor signal wire shorted to ground, low resistance, or sensor malfunction.)
P0017: Coolant Temperature Sensor Circuit Low Input. (Possible causes: Sensor signal wire open to ground, excessive resistance, or sensor malfunction.)
P0115: Coolant Temperature Sensor Circuit Malfunction.
P0116: Coolant Temperature Sensor Circuit Range/Performance Problem.
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How to reset and replace coolant temperature sensor
To reset the coolant temperature sensor, you don't typically need to perform a specific reset procedure. The sensor will automatically reset itself once the issue that triggered the warning or error condition has been resolved. This can happen when the coolant temperature returns to normal or when the underlying problem is fixed.
However, if you want to reset the engine control unit (ECU) to clear any stored error codes associated with the coolant temperature sensor, the following are the general steps:
Locate the vehicle's battery: Find the vehicle's battery in the engine bay or trunk. Ensure you have the necessary tools and take appropriate safety precautions.
Disconnect the negative battery terminal: Use a wrench or socket to loosen and remove the negative (-) battery terminal connection. This is usually indicated by a black cable or a negative symbol (-).
Wait for a few minutes: Leave the battery disconnected for about 5 to 10 minutes. This allows the ECU to discharge any stored power and reset its internal memory.
Reconnect the negative battery terminal: After the waiting period, reconnect the negative battery terminal and tighten it securely.
Start the engine: Start the engine and check if the coolant temperature sensor warning light is still illuminated. If the issue has been resolved, the warning light should no longer be present. If it persists, there may be an ongoing problem that requires further diagnosis.
Now, regarding the replacement of the coolant temperature sensor, here are the general steps:
Locate the sensor:The coolant temperature sensor is typically located near the engine block, cylinder head, or thermostat housing. Refer to the vehicle's service manual or consult a reliable online resource to find the specific location for your vehicle.
Disconnect the electrical connector: Carefully disconnect the electrical connector from the sensor. This may involve pressing or releasing a clip or tab.
Remove the sensor: Depending on the sensor's design, you may need a wrench or socket to unscrew and remove it from its mounting location. Be cautious not to damage surrounding components or the sensor itself during removal.
Install the new sensor: Take the new coolant temperature sensor and thread it into the mounting location by hand. Use a wrench or socket to tighten it securely, but avoid overtightening.
Reconnect the electrical connector: Attach the electrical connector to the new sensor until it clicks into place. Ensure a secure connection.
Test the new sensor: Start the engine and monitor the coolant temperature gauge or warning light to ensure the new sensor is functioning properly. Additionally, you can use a diagnostic tool to check if any error codes related to the coolant temperature sensor are present.
3 FAQ of coolant temperature sensor
Q: Is it OK to drive without coolant temperature sensor?
A: No, it is not recommended to drive without a coolant temperature sensor. The coolant temperature sensor provides crucial information about the engine's temperature, allowing the engine control unit (ECU) to make necessary adjustments. Without the sensor, the ECU won't be able to monitor the engine's temperature accurately, leading to potential issues such as overheating, poor fuel efficiency, and engine damage. It is essential to have a functioning coolant temperature sensor to ensure the engine operates within the optimal temperature range and to prevent potential damage or performance problems.
Q: Is it bad to drive with bad coolant temp sensor?
A: Driving with a bad coolant temperature sensor is not recommended. A faulty sensor can result in inaccurate temperature readings, leading to problems such as engine overheating, improper fuel mixture, reduced performance, and potential engine damage. It can also cause the engine to run inefficiently, leading to increased fuel consumption. Ignoring or neglecting a malfunctioning coolant temperature sensor can have detrimental effects on the engine's performance and longevity. It is advisable to address the issue promptly and have the sensor replaced to ensure optimal engine operation.
Q: How often do you need to replace coolant temperature sensor?
A: The replacement interval for a coolant temperature sensor can vary depending on several factors such as the vehicle's make and model, driving conditions, and the sensor's quality. In general, coolant temperature sensors are designed to be durable and reliable, and they typically have a long service life.
However, like any electronic component, the coolant temperature sensor can still fail over time due to wear and tear or other factors. If you experience symptoms of a malfunctioning coolant temperature sensor or encounter related issues, it is recommended to have it inspected by a qualified mechanic. They can determine if the sensor needs replacement based on its condition and diagnostic tests.
