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P0115 Toyota Code - Engine Coolant Temperature Circuit Malfunction

Quick Answer

The engine coolant temperature sensor is used to monitor the engine coolant temperature. Common causes include Low engine coolant level, Faulty Engine Coolant Thermostat, Faulty Engine Coolant Temperature (ECT) sensor. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P0115 Toyota indicates Engine Coolant Temperature Circuit Malfunction.
Common causes
Common causes include Low engine coolant level, Faulty Engine Coolant Thermostat, Faulty Engine Coolant Temperature (ECT) sensor.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
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Code Popularity 65,043
How popular is this code, among other codes? Medium
What is this?
Table of contents Created and updated by William Orellana on Aug 23, 2022
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Code P0115 Toyota Description

The engine coolant temperature sensor is used to monitor the engine coolant temperature. The engine coolant temperature sensor has a thermistor with a resistance that varies according to the temperature of the engine coolant. When the coolant temperature is low, the resistance in the thermistor increases. When the temperature is high, the resistance drops. These variations in resistance are reflected in the output voltage from the sensor. The Engine Control Module (ECM) monitors the sensor voltage and uses this value to calculate the engine coolant temperature. When the sensor output voltage deviates from the normal operating range, the ECM interprets this as a fault in the engine coolant temperature sensor circuit and stores a Diagnostic Trouble Code (DTC).
OBDII Code P0115 Toyota - Engine Coolant Temperature Circuit Malfunction - AutoCodes.com
P0115 Toyota Code - Engine Coolant Temperature Circuit Malfunction
What does this mean?

What are the Possible Causes of the DTC P0115 Toyota?

  • Low engine coolant level
  • Faulty Engine Coolant Thermostat
  • Faulty Engine Coolant Temperature (ECT) sensor
  • Engine Coolant Temperature sensor harness is open or shorted
  • Engine Coolant Temperature sensor circuit poor electrical connection
  • Faulty Engine Control Module (ECM)

How to Fix the DTC P0115 Toyota?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

Start by checking the engine coolant level at the coolant reservoir, a low level may indicate a coolant leak. If the coolant level is correct, you should replace the Engine Coolant Temperature (ECT) sensor to fix the problem. The Engine Coolant Thermostat must be replaced every time there is a repair with the coolant system.









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What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0115 Toyota code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P0115 Toyota code?

Need more information on how to fix the P0115 Toyota code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0115 Toyota code diagnosed by a professional: Find a repair shop in your area

Information for Specific Toyota Models

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0115 Toyota Code

1. What are the common symptoms of OBDII code P0115 in a Toyota?

- Common symptoms include engine overheating, poor fuel economy, rough idling, and a check engine light illuminated on the dashboard.

2. What are the possible causes of the Engine Coolant Temperature Circuit Malfunction in a Toyota?

- Possible causes include a faulty engine coolant temperature sensor, damaged wiring or connectors in the coolant temperature circuit, low coolant level, or a malfunctioning engine control module.

3. How can I diagnose the OBDII code P0115 in my Toyota?

- You can diagnose the code by using an OBDII scanner to read and interpret the trouble code, checking the coolant level and quality, inspecting the wiring and connectors around the coolant temperature sensor, and testing the sensor itself for proper functionality.

4. Can a faulty engine coolant temperature sensor be repaired, or does it need to be replaced?

- In most cases, a faulty engine coolant temperature sensor will need to be replaced to resolve the P0115 code. Repairing the sensor is not recommended as replacement ensures proper functionality and reliability.

5. Are there any DIY repair tips for fixing the Engine Coolant Temperature Circuit Malfunction in a Toyota?

- DIY repair tips include checking and cleaning the connectors and wiring related to the coolant temperature sensor, ensuring the coolant level is adequate, and verifying proper sensor installation.

6. Will driving with the OBDII code P0115 in a Toyota cause any further damage to the vehicle?

- Continuing to drive with the P0115 code may lead to engine overheating, reduced fuel efficiency, and potential long-term damage to engine components. It is recommended to address the issue promptly.

7. Can resetting the check engine light make the OBDII code P0115 disappear permanently?

- Resetting the check engine light may temporarily clear the code, but if the underlying issue causing the P0115 code is not addressed, the code is likely to reappear once the vehicle is driven again.

8. How long does it typically take to repair the Engine Coolant Temperature Circuit Malfunction in a Toyota?

- The repair time can vary depending on the exact cause of the issue, but in most cases, it can take anywhere from 1 to 3 hours to diagnose and resolve the P0115 code in a Toyota.

9. Is it safe to drive my Toyota with the check engine light on due to the P0115 code?

- While driving with the check engine light on is possible, it is not recommended as the underlying issue may worsen over time. It is best to address the problem promptly to avoid potential damage to the vehicle.

10. Can extreme weather conditions affect the occurrence of the OBDII code P0115 in a Toyota?

- Extreme weather conditions can impact the engine coolant temperature readings and potentially trigger the P0115 code. It is important to monitor the vehicle's temperature in such conditions and address any issues promptly.

Discuss the causes and fixes for P0115 Toyota OBDII Code

Submit a New Comment

  • Any advice on why my 1998 Toyota 4 runner 2.7 engine wouldn't start until I try to crank it up 10 times? Then it would start?

    Reply to Comment

    • The P0115 - Engine Coolant Temperature (ECT) Circuit Malfunction code on your 1998 Toyota 4Runner with a 2.7L engine indicates an issue with the coolant temperature sensor or its circuit. Since your vehicle takes multiple attempts to start, it's likely that the engine control module (ECM) isn't getting accurate temperature readings, which can affect fuel delivery and ignition timing.

      Possible Causes of P0115 and Hard Starting:

      1. Faulty Engine Coolant Temperature Sensor (ECT):

        • A malfunctioning ECT sensor may send incorrect data to the ECM, causing it to miscalculate the fuel mixture—resulting in difficulty starting, especially when the engine is cold or hot.

      2. Wiring or Connector Issues:

        • Corroded or damaged wires and connectors to the ECT sensor can lead to intermittent signal loss, requiring multiple cranks before the ECM gets a valid reading.

      3. Thermostat Issues:

        • If the thermostat is stuck open or closed, it can affect coolant temperature readings, leading to incorrect engine operation.

      4. Incorrect Fuel Mixture:

        • A faulty ECT sensor can make the ECM think the engine is colder or hotter than it actually is, causing an overly rich or lean fuel mixture that makes starting difficult.

      5. Failing ECM (Rare but Possible):

        • In some cases, a failing ECM could misinterpret sensor data, although this is less likely compared to sensor or wiring issues.

      Troubleshooting Steps:

      1. Check the ECT Sensor:

        • Locate the ECT sensor (usually on the engine block or thermostat housing).
        • Inspect for corrosion, damage, or loose connections.
        • Use a multimeter to check the sensor resistance at various temperatures (compare with factory specs).

      2. Inspect Wiring and Connectors:

        • Check the wiring harness leading to the ECT sensor for frayed wires or poor connections.
        • Disconnect the sensor and inspect for bent pins or corrosion.

      3. Test Cold Start Operation:

        • Try disconnecting the ECT sensor before attempting to start the engine; the ECM should default to a backup setting. If the engine starts more easily, the sensor is likely faulty.

      4. Check for Thermostat Issues:

        • If the engine takes too long to warm up or overheats, the thermostat might need replacement.

      5. Clear Codes and Test:

        • After replacing or fixing the sensor, clear the code with an OBDII scanner and observe if the starting issue persists.

      Recommended Fix:

      If the ECT sensor or wiring is faulty, replacing the sensor and ensuring good connections should resolve the starting issue. The sensor is relatively inexpensive and a common failure point on older Toyotas.

      Let us know if you need more guidance or if any of these steps help resolve the issue!

      Reply to Comment
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