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Engine-Codes – Subaru – P1490 Subaru

P1490 Subaru Code - Thermostat Malfunction

Quick Answer

The P1490 code in a Subaru indicates a thermostat malfunction. Common causes include Thermostat stuck open or closed: The thermostat can get stuck in either position, preventing it from regulating the engine's temperature properly, Faulty temperature sensor: A malfunctioning temperature sensor can send incorrect signals to the thermostat, causing it to malfunction, Coolant leaks: Low coolant levels can affect the thermostat's performance. 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
P1490 Subaru indicates Thermostat Malfunction.
Common causes
Common causes include Thermostat stuck open or closed: The thermostat can get stuck in either position, preventing it from regulating the engine's temperature properly, Faulty temperature sensor: A malfunctioning temperature sensor can send incorrect signals to the thermostat, causing it to malfunction, Coolant leaks: Low coolant levels can affect the thermostat's performance.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 06, 2024
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Code P1490 Subaru Description

The P1490 code in a Subaru indicates a thermostat malfunction. The thermostat is a crucial component of the vehicle's cooling system, responsible for regulating the engine's temperature by controlling the flow of coolant. When the thermostat malfunctions, it can lead to overheating or overcooling of the engine, which can cause serious damage if not addressed promptly. This code typically points to a problem with the thermostat itself, such as being stuck in the open or closed position, or issues with the temperature sensor.

OBDII Code P1490 Subaru - Thermostat Malfunction
P1490 Subaru Code - Thermostat Malfunction

Common Causes of P1490 Subaru

  1. Thermostat stuck open or closed: The thermostat can get stuck in either position, preventing it from regulating the engine's temperature properly.
  2. Faulty temperature sensor: A malfunctioning temperature sensor can send incorrect signals to the thermostat, causing it to malfunction.
  3. Coolant leaks: Low coolant levels can affect the thermostat's performance.
  4. Electrical issues: Wiring or connection problems can also lead to thermostat malfunctions.

Symptoms of P1490 Subaru

  1. Engine overheating: One of the most common symptoms of a faulty thermostat is the engine running hotter than normal.
  2. Poor fuel economy: A malfunctioning thermostat can cause the engine to run inefficiently, leading to decreased fuel economy.
  3. Heater not working: If the thermostat is stuck open, the heater may not produce hot air as it should.
  4. Check engine light: The P1490 code will trigger the check engine light on the dashboard.

How to Fix P1490 Subaru

  1. Perform a diagnostic scan: Use a diagnostic tool to confirm the P1490 code and verify the thermostat malfunction.
  2. Replace the thermostat: Remove the old thermostat and install a new one, ensuring it is functioning correctly.
  3. Check coolant levels: Top up the coolant levels and check for any leaks that may have contributed to the issue.
  4. Test the system: Start the engine and monitor the temperature to ensure the thermostat is working properly.
  5. Clear the code: Use the diagnostic tool to clear the P1490 code from the vehicle's computer.

Cost to Fix P1490 Subaru

The cost of repairing a thermostat malfunction in a Subaru can vary depending on the specific model and year of the vehicle. Typically, the parts required for this repair, such as a new thermostat, gasket, and coolant, can range from $50 to $150. Labor costs can add another $100 to $200 to the total, bringing the estimated total repair cost to between $150 and $350. It's important to note that these are rough estimates, and actual costs may vary based on the factors mentioned earlier.

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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 P1490 Subaru Code

1. What does the OBDII code P1490 mean in a Subaru?

P1490 on a Subaru indicates a "Thermostat Malfunction," meaning the engine's cooling system is not maintaining proper temperature due to an issue with the thermostat.

2. What are the common symptoms of code P1490 in a Subaru?

Symptoms may include an illuminated check engine light, fluctuating engine temperatures, poor heater performance, or the engine running too cold or hot.

3. What causes the P1490 code to appear in a Subaru?

Common causes include a stuck-open or stuck-closed thermostat, a failing thermostat sensor, low coolant levels, or wiring and electrical issues related to the thermostat.

4. Can I drive my Subaru with a P1490 code?

Driving with this code is not recommended, as an improperly functioning thermostat can lead to engine overheating or inefficient operation, potentially causing long-term damage.

5. How do I diagnose the P1490 code on a Subaru?

Start by visually inspecting the thermostat, checking for stuck positions or leaks. Verify proper coolant levels, and use a scan tool to monitor temperature sensor readings.

6. What is the most common fix for the P1490 code in a Subaru?

The most common fix is replacing a faulty thermostat. Ensuring the new thermostat meets OEM specifications is crucial for proper operation.

7. Can low coolant levels trigger the P1490 code on a Subaru?

Yes, low coolant levels can affect the thermostat's operation and trigger the code. Always check and top off coolant to the proper level.

8. Is the P1490 code related to the engine temperature sensor in a Subaru?

While the code primarily refers to the thermostat, a malfunctioning engine temperature sensor can also contribute by providing incorrect readings.

9. How much does it cost to fix the P1490 code on a Subaru?

Repair costs can range from $50 to $250, depending on whether you replace a thermostat or address additional issues like coolant leaks or sensor problems.

10. Can a faulty thermostat affect fuel efficiency in a Subaru?

Yes, a malfunctioning thermostat can cause the engine to run too cold or too hot, reducing fuel efficiency and overall performance.

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