Are there 2 coolant temperature sensors?

Yes, in many vehicles there are typically two distinct coolant temperature sensors: one feeds the engine control unit (ECU) to manage fuel, ignition, and emissions, and a second reports coolant temperature to the dashboard gauge. It's not universal, though; some cars use a single sensor that serves both functions, while others can have more than two in special cooling configurations.

Two-sensor configurations are common

Many manufacturers opt for separate sensors to keep engine sensing and driver information independent, improving diagnostics and gauge accuracy. The two-sensor setup often places a sensor at the thermostat housing or engine block for the ECU, and another sensor at the cylinder head or near the intake manifold for the dash gauge.

The following are typical arrangements you might encounter across brands:

• Engine coolant temperature sensor (ECT) for the ECU: provides temperature data used for fuel mixture, ignition timing, and emissions controls.


• Coolant temperature sender or sensor for the dashboard gauge: provides a reading displayed to the driver, usually connected to the instrument cluster.


• In some engines, an additional third sensor may exist for a separate cooling loop (for turbochargers, diesel heaters, or dual-circuit systems), but this is less common.

In practice, not every vehicle uses two sensors. Check your owner's manual or service documentation for your specific model to confirm the layout.

Single-sensor configurations

Some vehicles combine functions into a single sensor or rely on the ECU to drive the gauge using the same data. This can simplify wiring but can complicate diagnostics if the gauge reads incorrectly while the ECU data is accurate.

• One engine coolant temperature sensor feeds the ECU, and the dashboard gauge is driven by the ECU output or a shared data line.


• In older or budget models, a single sensor may provide data to both the ECU and the instrument cluster without a separate sender.

Always verify with the service manual: the presence or absence of a second sensor varies by make, model, and generation.

How to identify and test sensors in your vehicle

To determine exactly how many sensors your car uses and whether they’re functioning, follow these steps. This helps you diagnose issues related to temperature readings and drivability:

1. Inspect the engine bay and locate sensors near the thermostat housing and along the engine block or cylinder head. Look for two distinct sensors with different connectors.


2. Check the wiring harnesses and connector types; a two-sensor setup often has two different connectors, one for each sensor.


3. Consult the vehicle’s service manual or a repair database to confirm the expected layout for your exact make/model/engine code.


4. Use an OBD-II scanner to observe the engine coolant temperature (ECT) reading from the ECU. Compare it with the temperature shown by the dash gauge if available.


5. If possible, test sensor resistance/voltage at varying temperatures (cold vs hot) following the factory specs. This typically requires removing the sensor and testing with a multimeter or specialized tool.


6. Replace any sensor with readings out of spec or with erratic data, after verifying wiring and grounds are clean and secure.

Note: Always follow safety precautions when working with hot engine components and disconnect the battery before performing electrical testing.

What happens if sensors fail?

Failing coolant temperature sensors can affect fuel economy, idle stability, starting in cold weather, and the accuracy of the temperature gauge. In some cases, the ECU may default to a safe temperature reading, causing rich or lean fuel mixtures, increased emissions, or poor cold-start behavior. A diagnostic code or a fluctuating gauge is often the first clue.

If your vehicle has two sensors and one fails, you may still drive, but the gauge could read incorrectly or the ECU may rely on a fallback value. Replacing the faulty sensor(s) with OEM or equivalent parts is recommended, and professional diagnostics can confirm the cause.

Summary

Across vehicles, having two coolant temperature sensors is common but not universal. The split can provide independent data for the ECU and the driver display, or be a single-sensor arrangement in older or simpler designs. Always verify with your manual and consult a technician if you notice temperature readings or performance problems.

What are the two types of temperature sensors?

Types of Temperature Sensors

• Contact Temperature Sensors – As their name implies, these sensors have to be in direct contact with the object whose temperature is being measured.
• Non-Contact Temperature Sensors – Unlike conventional contact sensors, non-contacts don't require physical contact with the object.

How to test a 2 wire coolant temperature sensor?

To test a two-wire coolant temp sensor, unplug it from the engine and use a multimeter set to resistance mode to measure the ohms between its two terminals. You should get a high resistance reading when the sensor is cold and a much lower reading when it is heated. If the reading is infinite (OL) when cold, or doesn't change when heated, the sensor is likely faulty.
 
This video demonstrates how to test a coolant temperature sensor using a multimeter: 1mCarsNToysYouTube · Oct 30, 2014
Step 1: Set up and prepare the sensor 

• Locate the coolant temperature sensor on your engine, typically in the cylinder head or thermostat housing. 
• Unplug the sensor's electrical connector. 
• Set your multimeter to measure resistance in Ohms (Ωcap omegaΩ). 

Step 2: Test the sensor's resistance at room temperature 

• Touch one multimeter probe to each of the sensor's two terminals. 
• Note the resistance reading. It should be a specific high value for a cold sensor. If the reading is "OL" (open line) or infinite, the sensor is likely bad, even if cold, and you don't need to proceed. 

Step 3: Test the sensor's resistance when hot 

• Carefully place the sensor tip (or the entire sensor, if possible without submersion) into a container of hot water. 
• Note the new resistance reading once the sensor has been in the hot water for a few seconds. The resistance should be significantly lower than the cold reading. 

Step 4: Interpret the results

• Compare your readings to the specifications for your vehicle, which can be found in the owner's manual or online. A common example is a reading of around 2000−30002000 minus 30002000−3000 ohms when cold and 200−300200 minus 300200−300 ohms when hot at 90°C90 degrees cap C90°𝐶. 
• If the resistance was infinite when cold or didn't decrease significantly when heated, the sensor is faulty and needs to be replaced. 
• If your readings are within the expected range, the sensor is working correctly and the problem lies elsewhere. 

What are the two coolant sensors?

You are entirely likely to have two sensors, one for radiator temperature and one for engine temperature. The engine sensor tells the ECU what temperature the engine is working at. The radiator sensor tells the fan control module when to switch on the radiator fans, and how fast to run them.

What are the different types of coolant temperature sensors?

There are four main temperature sensors used today in modern-day electronics: Negative temperature coefficient (NTC) thermistors, resistance temperature detectors (RTDs), thermocouples, and semiconductor-based integrated (IC) sensors.