Will the check engine light come on if the thermostat is bad?

Author: Alford Halvorson  |  Last update: Sunday, May 18, 2025

When your thermostat doesn;t respond to temperature conditions in your cooling system or gets stuck in either the open or closed position, it may cause a Check Engine Light to turn on. Ensure your thermostat is in good condition in order to prevent engine damage from excess heat.

Would a bad thermostat throw a check engine light?

Yes, if the thermostat is not working correctly, it will throw a code and turn on the check engine light. The thermostat is responsible for regulating the engine's coolant temperature. If it is not working properly, the engine can overheat.

Will you get a code if your thermostat is bad?

P0128 is an extension of OBD-II code P0 which indicates a problem with your car's coolant thermostat.

How does a car act when the thermostat is bad?

You Notice Erratic Temperature Changes

If you notice sudden and erratic temperature changes from cold to hot or hot to cold, then it could be a sign that your thermostat has stopped working correctly. Get your vehicle inspected if you notice these extreme temperature changes in your vehicle interior.

How much does it cost to fix an engine thermostat?

Car thermostat replacement time is 30 to 60 minutes, depending on the make of the car. It will cost you around $190 to $350, including labor. Thermostat repairs usually take more time, requiring extra time to diagnose and analyze the vehicle's thermostat.

Can Low Coolant Cause Check Engine Light?

Can I drive a car with a bad thermostat?

If you drive with a bad thermostat, your car could overheat, causing severe and expensive engine damage. And while it's technically possible to drive without a thermostat, we don't recommend it. Your car will not reach an acceptable operating temperature, resulting in higher fuel consumption and excessive engine wear.

Can I replace my thermostat myself?

In most cases, installing a new thermostat is a relatively simple do-it-yourself project that can result in improved comfort and convenience and one that can help you save energy.

How do I know if my car needs a new thermostat?

Signs My Car's Thermostat Is Going Bad or Has Failed Completely
  1. Odd Temperature Gauge Readings. Your temperature gauge should register cold when you first start your car and slowly build up to normal as the engine warms up. ...
  2. Air Temperature Changes. ...
  3. Coolant Leaks. ...
  4. Strange Sounds. ...
  5. Heater Problems.

How do I know if my water pump or thermostat is bad?

Here are signs you've got a bad pump or thermostat.
  1. Corroded Cooling System Parts. Both of these cooling system parts can get corroded if they start to leak slowly. ...
  2. Leaking Engine Coolant. ...
  3. Erratic Temperature Changes. ...
  4. Poor Coolant Circulation. ...
  5. Overheating Constantly.

What is the life expectancy of a car thermostat?

A car thermostat is designed to last a long time – typically around 100,000 miles or 10 years. However, various factors can impact its lifespan. First, driving conditions play a role. If you regularly drive in hot weather or stop-and-go traffic, your thermostat may suffer additional stress.

How can I test if my thermostat is bad?

When you set the thermostat above or below the current room temperature, you should hear a click, and the AC or furnace should kick on almost immediately. If you make changes at the thermostat and nothing happens, that's the first sign you have a bad thermostat.

How to unstick a car thermostat?

This is an easy problem to solve yourself by simply removing the plastic outer casing and, with a very soft brush, delicately brushing off its coil and contact surfaces. It is most effective to clean the thermostat first at its lowest setting, then again at its highest setting.

Will a code reader detect a bad thermostat?

Will a code reader detect a bad thermostat? A code reader can detect issues related to a bad thermostat by identifying specific trouble codes, such as P0128 or P0597, which indicate problems with the thermostat or the engine's temperature regulation.

Will check engine light go off after replacing thermostat?

In most cases, successfully repairing the issue that caused your light to come on will cause the check engine light to turn off automatically—but only after 10 to 20 “cycles”.

What happens to engine when thermostat is not working?

Due to corrosion or aging, your car's thermostat can get stuck in a closed position. If this happens, the thermostat will not let the coolant reach the radiator, and, as mentioned above, the engine will overheat, causing severe damage. One of the lesser-known issues is the polar opposite of overheating.

How do I know if my thermostat or sensor is bad?

Symptoms of bad temperature sensor
  1. Erratic Readings. Sudden jumps or drops in temperature readings. ...
  2. Open Circuit: Display shows a very high or infinite temperature. ...
  3. Short Circuit: Display shows a very low or negative temperature. ...
  4. Drift: ...
  5. Noise or Interference: ...
  6. Physical Damage:

How much does it cost to replace a thermostat?

Replacing a Thermostat. You'll pay between $15 and $300 for the unit in addition to labor ($65 to $100 per hour) to replace an old thermostat with a new one. However, installing a brand-new thermostat is more involved and, therefore, more expensive.

How many hours does it take to replace a thermostat in a car?

How long does it take to replace a car thermostat? It depends on access on the car. Some are two bolts and easily accessible. Others have very limited space and require taking a lot of other parts off, An hour on an easy car with refilling coolant and running it to operating temperature, checking coolant.

What are the symptoms of a thermostat not opening?

High temperature readings

The main symptoms of a failing thermostat are related to engine overheating. It can be easily noticed because the temperature gauge in the vehicle will probably read unusually high. This can be caused by the valves being stuck in a closed position.

Will a bad thermostat throw a code?

While there is a small chance that there is an issue with the running temperature of your engine, by far the most common issue with trouble code P0128 is a faulty thermostat. The exact location of the thermostat and issues related to a damaged thermostat may vary depending on your vehicle.

Can I replace my car thermostat myself?

Luckily, it only takes a few minutes and a couple of tools to change your thermostat yourself. Our guide will show you how to remove the bad thermostat and replace it with a new one!

How expensive is it to move a thermostat?

Moving a Thermostat: If the required wiring exists at the desired location, moving a thermostat may cost as little as $65. However, moving the unit can entail installing new wiring and cutting and patching drywall, so the project can cost up to $450.

How do I know if I need a new thermostat?

If your thermostat has fresh batteries but suddenly lacks power, flashes, or isn't responsive to adjustments, it may need replacement. If resetting the thermostat doesn't resolve the problem, you may have wiring problems or faulty components causing your thermostat to not turn on.

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