Unleash Your Engine’s Potential: How to Reset Coolant Temp Sensor

reset coolant temp sensor
Table of Contents

Knowing how to reset coolant temp sensor in your vehicle is essential for maintaining optimal engine performance and preventing damage to your vehicle. A malfunctioning sensor can significantly impact your vehicle’s overall performance, leading to various issues. What are common faults with coolant temperature sensors? How to tell if your coolant temp sensor is bad? In this article, we will explore the process of resetting the coolant temp sensor and address common questions related to its functionality, symptoms of a faulty sensor, testing methods, and the importance of proper maintenance. So, let’s delve into the details and explore the effective techniques for resetting a coolant temperature sensor.

What's the Coolant Temp Sensor?

The coolant temp sensor (CTS), also referred to as the engine coolant temperature sensor, plays a pivotal part in the engine operating system of a vehicle.

The coolant temp sensor is typically a thermistor, its resistance varies with temperature. It has a probe that is immersed in the coolant, as the temperature of the coolant fluctuates, the resistance of the sensor alters accordingly. This change in resistance is then converted into a voltage signal by the engine control module.

Source: What is a Coolant Temperature Sensor by Automotive Engineering

Where Is the Coolant Temp Sensor Located?

The specific location of the coolant temp sensor can vary depending on the vehicle’s brand and model. However, in general, you can typically find the coolant temperature sensor in proximity to the thermostat within the cylinder head or block, or on the thermostat housing. Additionally, you may find the sensor positioned on the engine block, cylinder head, or on the intake manifold.

What Is the Function of a Coolant Temperature Sensor?

A coolant temp sensor measures the temperature of the engine coolant and sends this critical information to the engine control module (ECM). With this data, the ECM makes informed decisions such as activating the cooling fan, adjusting fuel injection timing, ignition timing, and managing variable valve timing. By utilizing the information from the coolant temp sensor, the engine can function at its peak performance and efficiency, while simultaneously safeguarding against overheating and potential engine harm.

What Are the Various Types of Coolant Temperature Sensors?

The market offers several variants of coolant temperature sensors, each with its own characteristics. The most prevalent types include:

  • Thermistors – Thermistors are the prevailing type of coolant temperature sensors in contemporary vehicles. The changes in resistance correspond to alterations in the engine coolant temperature, enabling precise temperature measurement by the ECM.
  • Resistance Temperature Detectors (RTDs) – RTDs are constructed using materials that suffer changes in resistance as temperature shifts. Platinum is the generally employed material in RTDs. While RTDs offer enhanced delicacy compared to thermistors, they’re also relatively more expensive.
  • Thermocouples – These sensors generate a voltage proportionate to the temperature difference between two dissimilar metals. They are ideal for use in harsh situations because of their great accuracy and capacity to measure temperatures at extremely high levels.
  • Bi-metallic strip sensors – Bi-metallic strip sensors function by utilizing two metals with distinct coefficients of thermal expansion. As the engine coolant temperature changes, the bi-metallic strip bends, inducing a resistance alteration that can be measured by the ECM. However, these sensors are less precise than other types and are not commonly employed in modern vehicles.

What Happens if the Coolant Temperature Sensor Is Bad?

Symptoms Of A Bad Coolant Temperature Sensor:

Overheating Engine

A malfunctioning coolant temp sensor may send incorrect data to the ECM, resulting in the failure to engage cooling fans or not providing enough fuel to the engine, which may cause the engine to overheat.

Poor Fuel Economy

When the ECM does not receive accurate temperature information, it may struggle to adjust the fuel mixture properly. As a consequence, the engine may consume more fuel than necessary, leading to decreased fuel economy.

poor fuel economy

Check Engine Light Turns On

A faulty coolant temp sensor can trigger the activation of the check engine light. The ECM may detect irregularities in the sensor’s signal and illuminate the light as a warning.

check engine light turns on

Black Smoke Emitted from the Exhaust

A bad coolant temperature sensor can result in excess fuel being burned, resulting in the emission of black smoke from the exhaust.

black smoke emitted from the exhaust

Intermittent Misfires

If the coolant temp sensorr sends erratic signals to the ECM, the ECM may not be able to properly adjust the fuel mixture. This can cause the engine to misfire.

Coolant Temperature Gauge Fluctuations

A faulty coolant temperature sensor can lead to erratic readings on the coolant temperature gauge. The gauge may display temperatures that are too high, too low, or fluctuate unpredictably.

Engine Running Rough

A defective coolant temperature sensor can disrupt the ECM’s ability to properly adjust the fuel mixture or ignition timing, resulting in rough engine operation.

Engine Stalls

A failing engine coolant temp sensor can provide inaccurate temperature information to the ECM, leading to stalling or hesitation during acceleration.

How to Diagnose a Coolant Temperature Sensor Issue

How to Test Coolant Temp Sensor with Multimeter?

To test the operation of a coolant temperature sensor using a multimeter, follow these step-by-step instructions:

  1. Locate the coolant temperature sensor: Find the coolant temp sensor, usually located near the thermostat in the engine block. Refer to your vehicle’s owner’s manual or reliable online resources for help identifying its precise location.
  2. Disconnect the electrical connector: Safely disconnect the electrical connector from the coolant temp sensor.
  3. Set up the multimeter: Configure your multimeter on the ohms setting. This setting allows you to measure electrical resistance directly.
  4. Measure the resistance: Touch the two multimeter leads carefully to the terminals on the coolant temperature sensor while it’s still connected. Check the resistance value displayed on the multimeter. The reading should match a specific resistance value associated with the engine coolant temperature range. To find the correct resistance values based on various temperatures, refer to your vehicle’s service manual.
  5. Compare the results: Compare the resistance reading obtained from the multimeter with the recommended values outlined in your vehicle’s service manual. If the measured resistance falls outside the suggested range, this indicates a potential fault in the coolant temp sensor that requires replacement.
  6. Reconnect the electrical connector: Once you finish testing the coolant temp sensor, securely reconnect the electrical connector to the sensor, ensuring proper alignment and connection.

How to Test Coolant Temp Sensor Without Multimeter?

There are alternative methods to test your coolant temp sensor if you don’t have a multimeter. To visually check and evaluate the sensor, follow these procedures. It’s vital to remember that utilizing a multimeter may provide more accurate results than visual inspection and observation.

  • Check for physical damage: Look for visible signs of damage on the sensor, such as cracks or breaks. Damaged sensors need to be replaced.
  • Inspect electrical connections: Ensure that the electrical connections leading to the sensor are firmly attached and free of corrosion or dirt buildup. If they are dirty or corroded, clean them with a wire brush or electrical contact cleaner.
  • Check for coolant leaks: Inspect the area around the coolant temp sensor for any signs of coolant leaks or seepage. A leak can affect the sensor’s ability to provide accurate readings.
  • Start the engine: Start the engine, then look at the dashboard temperature display. As the engine heats up, the gauge ought to show a smooth and progressive rise. A sensor issue may be indicated if the gauge oscillates between two extremes or moves irregularly.
  • Monitor engine performance: Keep an eye on the engine’s performance when driving normally. Poor fuel efficiency, stalling, and other aberrant behavior might be brought on by a malfunctioning coolant temperature sensor.

What Causes a Coolant Temperature Sensor to Go Bad?

How do you know coolant temp sensor is bad? A coolant temperature sensor’s failure can result from a number of factors. Here are a few common reasons:

Electrical Problems

The coolant temp sensor is connected to the engine’s computer by a wiring harness. Damaged or corroded wiring can lead to inaccurate readings or sensor failure.

Physical Damage

The coolant temperature sensor is a small and delicate component. It can be susceptible to damage from impacts, vibrations, or other physical forces, resulting in malfunction or failure.


Accumulation of dirt, debris, or other contaminants on the coolant temp sensor can interfere with its proper functioning. This can lead to incorrect temperature readings and potential sensor failure.

Wear and Tear

Like any mechanical component, the coolant temp sensor can experience wear and degradation over time. Extended exposure to extreme temperature changes can contribute to its deterioration and eventual failure.


If the engine experiences excessive overheating, it can subject the coolant temperature sensor to high temperatures, potentially causing damage or failure.

Incorrect Installation

Improper installation of the coolant temp sensor or its associated wiring can lead to damage and subsequent failure. It is crucial to follow proper installation procedures to ensure optimal sensor performance.

Exposure to Chemicals

Antifreeze and other additives in the engine’s cooling system may be corrosive and harm the coolant temp sensor, causing failure or malfunction.

Manufacturing Defects

While uncommon, manufacturing defects can occur, resulting in a faulty coolant temperature sensor that may fail shortly after installation.

How to Reset Coolant Temp Sensor?

how to reset coolant temp sensor

How to reset engine coolant temperature sensor? There are two approaches to resetting a coolant temp sensor.

Method 1: Clear the fault code with an OBD-II scanner

1. Locate the OBD-II diagnostic port

Find the OBD-II diagnostic port in your vehicle, usually located under the dashboard or in the center console area.

2. Connect the OBD-II scanner

Plug the OBD-II scanner into the diagnostic port of your car.

3. Ignition on, but engine off

Turn on the ignition without starting the engine. This will power up the scanner and enable it to communicate with your car’s computer.

4. Scan for fault codes

Use the OBD-II scanner to scan your car’s computer for any fault codes, specifically related to the coolant temperature sensor.

5. Clear the fault code

If the scanner detects a fault code for the coolant temp sensor, follow the prompts on the scanner’s interface to clear the code from the car’s computer.

6. Turn off the ignition and disconnect the scanner

After clearing the fault code, turn off the ignition and disconnect the OBD-II scanner from the diagnostic port.

Method 2: Disconnect the sensor for a few minutes

1. Engine off and cooled down

Ensure that the engine is completely turned off and has cooled down before proceeding.

2. Locate the coolant temperature sensor

Refer to your car’s owner’s manual to locate the coolant temperature sensor in your specific vehicle.

3. Disconnect the electrical connector

Carefully disconnect the electrical connector that is attached to the coolant temp sensor. This will interrupt the sensor’s connection to the car’s electrical system.

4. Wait for a few minutes

Allow a few minutes for any residual electrical charges to dissipate and to clear temporary data stored in the car’s system.

5. Reconnect the electrical connector

After the waiting period, securely reconnect the electrical connector to the coolant temperature sensor.

6. Start the engine and monitor the temperature gauge

Start the engine and observe the temperature gauge on your car’s dashboard. The coolant temp sensor should recalibrate itself and provide accurate readings once again.

Selecting the appropriate method:

The most suitable method for resetting a coolant temperature sensor will depend on the specific make and model of your vehicle. Some cars have built-in procedures to reset fault codes related to the coolant temp sensor, while others necessitate the use of an OBD-II scanner. To determine the recommended method for your vehicle, consult your car’s owner’s manual or seek professional advice.

How to Fix Coolant Temp Sensor?

A coolant temperature sensor, like any other electronic component, can wear out over time, causing it to fail. If your coolant temp sensor fails, it may be difficult to detect and repair the problem. A defective coolant temp sensor, in many circumstances, cannot be repaired and needs to be replaced.

The reason that a coolant temp sensor cannot be fixed is that it is typically made up of several delicate electronic components that can be easily damaged during testing or repair attempts. Additionally, some sensors may require specialized equipment to test and diagnose effectively, which may not be available to the average person.

Therefore, if you suspect that your coolant temperature sensor is faulty, you should take your vehicle to a professional mechanic who can accurately diagnose the problem and replace the sensor if necessary.

When Should I Replace My Coolant Temp Sensor?

The replacement interval for a coolant temperature sensor is not set according to a specific schedule. Generally, these sensors have a lifespan of approximately 100,000 miles. However, the actual period might vary based on factors such as vehicle brand and model, driving behavior, and environmental conditions.

If you observe any indications of a faulty coolant temperature sensor, including the illumination of the check engine light, engine overheating, or rough engine performance, it is advisable to have the sensor inspected. Prompt attention and diagnosis by a professional can help identify any issues with the sensor and ensure optimal engine performance and reliability.

How to Replace an Engine Coolant Temperature Sensor?

Here is a step on how to replace a coolant temperature sensor:

  1. Locate the coolant temperature sensor
  2. Disconnect the electrical connector
  3. Remove the sensor
  4. Install the new sensor
  5. Connect the electrical connector
  6. Fill the cooling system with coolant
  7. Start the engine and check for leaks

FAQs on How to Reset Coolant Temp Sensor

Will a Coolant Temperature Sensor Throw a Code?

Yes, a coolant temperature sensor can trigger error codes. When the sensor is defective, it can transmit inaccurate information to the Engine Control Module. Consequently, the ECM may miscalculate the engine temperature, resulting in various issues.

What Is the Code for the Engine Coolant Temperature Sensor?

The specific error code that will be generated can vary depending on the make and model of your vehicle. However, there are several common codes associated with a faulty coolant temperature sensor, including:




Coolant Temperature Sensor Circuit Range/Performance


Coolant Temperature Sensor Circuit Low Input


Coolant Temperature Sensor Circuit High Input


Coolant Temperature Sensor Intermittent

These codes indicate potential issues related to the coolant temp sensor circuit and its input/output signals. When these codes are present, it is a clear indication that the Engine Control Module has detected irregularities in the coolant temperature sensor’s operation. If you encounter any of these error codes, it is advisable to have the coolant temp sensor and associated circuits inspected and, if necessary, replaced.

Can a Bad Coolant Temp Sensor Cause Hard Start?

Yes, a bad coolant temp sensor can cause a hard start. The coolant temperature sensor is responsible for sending the engine’s temperature information to the Engine Control Module. This data is used by the ECM to calculate the quantum of fuel to fit into the cylinders and the quantum of air to blend with the fuel. A hard start may result if the ECM is unable to receive accurate temperature information due to a malfunctioning coolant temp sensor.

What Happens if I Unplug Coolant Temperature Sensor?

Your car’s engine won’t be able to get precise temperature readings if you unplug the coolant temperature sensor. This may result in a variety of issues, such as:

  • Increased idle speed
  • The engine may overheat
  • Richer fuel mixture
  • The check engine light may come on
  • Poor engine performance
  • The car may lose power

Can I Drive My Car with a Bad Coolant Temperature Sensor?

It is not recommended to drive your car with a bad coolant temperature sensor. If the coolant temp sensor is faulty or sends incorrect signals to the ECM, it can cause various problems.

Can a Bad Coolant Temp Sensor Cause Rough Idle?

Yes, a faulty coolant temp sensorr can contribute to a rough idle.

The coolant temperature sensor helps the ECM determine the engine’s temperature, allowing it to adjust the air-fuel mixture for optimal combustion. If the sensor is faulty, it may send incorrect temperature readings to the ECM, resulting in an improper fuel mixture. This can lead to a rich (excess fuel) or lean (insufficient fuel) condition, both of which can cause a rough idle.

Are There 2 Coolant Temperature Sensors?

Yes, certain vehicles are equipped with two coolant temperature sensors.

Typically, one of the sensors is situated near the thermostat housing. Its primary role is to provide the Engine Control Module (ECM) with temperature information for efficient fuel mixture and ignition timing adjustments during cold starts in low ambient temperatures. This helps facilitate a faster engine warm-up.

The other coolant temperature sensor is commonly positioned in the engine block or cylinder head. Its purpose is to safeguard the engine by continuously monitoring the coolant temperature. This information is communicated to the ECM, assisting it in avoiding engine overheating and enabling the ECM to make the necessary adjustments to prevent potential damage.

Does the Coolant Sensor Control the Thermostat?

No, the coolant sensor does not control the thermostat. The thermostat is a mechanical mechanism that opens and shuts in response to the coolant temperature. The coolant sensor gives a signal to the Engine Control Unit, which decides whether or not the thermostat should be opened.

Is Temperature Sensor and Coolant Sensor the Same?

No, a temperature sensor and a coolant sensor are not the same. A temperature sensor is a broad term encompassing various sensors designed to measure temperature across different systems. A coolant sensor is purpose-built to provide precise measurements of the coolant temperature, enabling accurate monitoring and control of engine cooling performance.

Is It Expensive to Fix a Coolant Temperature Sensor?

The expense of repairing or replacing a coolant temperature sensor can fluctuate based on various factors. These factors include the vehicle’s make and model, the specific location of the sensor, and labor costs prevalent in your geographical area.

Typically, the cost of the coolant temp sensor itself is relatively affordable, falling within the range of $20 to $100. However, additional expenses may be incurred, including diagnostic fees for identifying the issue and labor charges for the installation process.

Do You Need to Drain Coolant to Change Coolant Temperature Sensor?

For the majority of autos, replacing the coolant temperature sensor does not need draining the coolant. However, if the sensor is in a tricky-to-reach place in your automobile, emptying the coolant could make the process simpler.

Consult the owner’s handbook for your automobile if you’re unsure whether you need to drain the coolant. The manual will typically specify whether or not you need to drain the coolant to change the coolant temp sensor.

Conclusion on How to Reset Coolant Temp Sensor

In summary, having the knowledge of how to reset coolant temp sensor is highly beneficial when addressing engine performance and temperature control issues. If you have any queries or concerns about your vehicle’s cooling system or coolant temperature sensor, it’s crucial to study the owner’s manual or get advice from a skilled repair.

By proactively maintaining your vehicle’s cooling system and promptly addressing any concerns, you can ensure a secure and pleasant driving experience. Remember, the proper functioning of the coolant temp sensor plays a significant role in maintaining optimal engine performance and preventing potential complications.

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