Why Is My Check Engine Light On in Hot Weather?

The check engine light is used to alert drivers of potential car issues. While this serves as a warning light to help prevent further car damage, some car owners have complained of seeing it when the temperature fluctuates. While the light comes on for some during the cold weather, others reportedly see it in hot weather.

And has even made rounds on many automotive forums. Thus, begging the question, why does the check engine light in hot weather come on? Follow me as I unveil some top reasons your CEL illuminates in high temperatures and how to fix it.

check engine light in hot weather

Why your check engine light turns on during the hot weather

The illumination of CEL points to a fault in your car; it could be something minor or major. However, knowing what triggered it in certain weather conditions will reduce panic and give you a clue on what to avoid.

But generally, the check engine light in hot weather might mean the cooling system, emission system, and circulation components are probably not working as they should. And the transmission and engine may still be experiencing overheating. Let’s look closely at common reasons the check engine light turns on in hot weather.

Fluid evaporation

Extreme temperature causes rapid evaporation of various fluids such as the engine oil, transmission fluid, and coolant. This results in fluid shortage, which in turn decreases cooling efficiency and proper lubrication. Invariably leading to engine overheating and even engine damage. And eventually triggering the CEL to come on

Note that these fluids can also be the reason the check engine light comes on when engine is cold. While fluid evaporation occurs in hot weather, freezing occurs in cold weather, which eventually restricts fluid movement.

Loosed or missing gas cap

A vehicle gas cap serves as a seal to prevent fuel fumes from leaving the gas tank and keep the system under the right pressure. Extreme heat will usually cause the fuel to evaporate quickly. Imagine when the cap is out of place.

When the cap is missing or not properly tightened, the hot atmosphere outside causes the fuel to expand and escape from the cap. This not only triggers the CEL to turn on but results in poor fuel economy and performance issues.

In cold weather, instead of evaporation, the gas will instead contract and also suck in vapor and eventually freeze. And trigger the CEL. This should answer those asking, can humidity cause check engine light to come on?

Failing oxygen sensors

The oxygen sensors, also called the O2 sensors, measure the amount of unburnt oxygen in your vehicle’s exhaust. The sensor sends this data to the ECU, which in turn uses it to determine the amount of fuel to push into the engine.

This sensor can go bad for several reasons, such as exhaust leaks, etc. However, in extremely hot weather, heat can damage the O2 sensors and cause them to malfunction. Invariably triggering the check engine light.

Cold weather is also an issue for this sensor. So don’t be surprised if you see the check engine light after driving in snow. The O2 sensor can stop working if covered in ice or snow.

Engine overheating

Hot climates usually make your engine run hotter than usual, leading to engine overheating. The ECM will tell you your engine is overheating by triggering the CEL.

Catalytic converter issues

The catalytic converter minimizes your car’s emissions. It does this by helping to convert toxic fumes to less toxic ones. In hotter climates, it may suffer from overheating, which can cause it to be less potent or fail. Because it doesn’t do its job as it should, the ECM will let you know by triggering the CEL. There are, however, other things that can cause the cat failure

Faulty spark plugs

The spark plugs ignite the air-fuel mixture in the combustion chamber so your car can start. In extremely high temperatures, these plugs can overheat, causing them to expand and contrast, leading to damage.

When the spark plugs fail to function as they should, it causes the engine to run rich or lean. Invariably, causing the check engine light to turn on. So, for those asking, can extreme heat cause check engine light? Now you know.

Clogged air filter

A car’s air filter helps trap contaminants so the engine remains clean. This filter, over time, can clog up. However, in hotter climates, it clogs faster since there is more dirt or pollen in the atmosphere. A clogged air filter can restrict airflow to the engine. Because the engine doesn’t get enough air, the ECM lets you know by triggering the check engine light.

Dirty mass air flow (MAF) sensor

The MAF sensor helps measure the amount of air entering the engine. During the hot months, this sensor tends to get dirty faster due to increased dirt and pollen in the air. A dirty mass air flow sensor will not function effectively, invariably triggering the CEL to turn on.

Cooling system issues

The cooling system ensures your engine runs cool, preventing engine overheating and potential engine damage. The radiator, for example, helps disperse heat from the engine with the help of the coolant and water, fan, water pump, thermostat, etc.

If any of these cooling system components is not functioning as it should, your engine will overheat and trigger the CEL to turn on. Picture this. In hot climates, the engine will usually run hotter than normal. Now imagine the things meant to cool it are out of place.

Weak battery

Extreme high temperature causes a rapid evaporation of your battery electrolytes. Eventually, this leads to decreased battery life and performance as well as susceptibility to corrosion and battery failure. When the battery voltage drops below the required threshold, your CEL will pop.

can hot weather cause check engine light to come on

How to prevent the check engine light from turning on in a hot climate

The most effective way to avoid CEL in hot weather is to ensure your engine and other car components remain cool. This can be done in several ways.

  • Park in a shaded area to prevent your car from direct sunlight
  • Ensure your cooling system (radiator, fan, coolant, etc) is working properly
  • Immediately have your car checked if you notice it’s running like crap. Continue driving it will also worsen things
  • One of the best ways to avoid CEL, whether in hot or cold weather, is to keep the gas cap tightened always.

Ensure your gas cap is replaced and properly tightened after visiting the fuel station. Most car users sometimes leave their gas cap on their roof or fail to tighten it well after filling their gas tank.

  • Air filters tend to clog faster in hot climates. You might need to replace or wash often
  • Monitor the MAF sensor more in hot climates and clean
  • You may need to change your spark plugs often or buy one that can withstand heat
  • Switch to engine oils that can withstand heat
  • The engine will definitely experience heat in hotter weather. However, ensuring your cooling system is working effectively can minimize engine overheating. This invariably reduces heat from affecting your O2 sensors and catalytic converter.

What to do when the check engine light comes on in hot weather

A few things are known to cause the CEL in hot weather. This includes bad spark plugs, clogged air filters, bad O2 sensors, etc. Technically, fixing those things should make the light go away. However, fixing based on guesses is not really cost-effective. To save you time and money, do it in this order

Scan for fault codes

Use an OBD II scanner to scan for error codes. These codes will tell you the exact component responsible for the CEL. Even if the light has disappeared, the codes will still be stored in your vehicle’s computer.

Clear fault codes

Clear the codes and see which comes back. The check engine light should disappear after clearing the codes; however, sometimes, the check engine light goes away itself.

Repair or adjust faulty components

With the result from the code reader, handle the items responsible for the CEL light. But generally, you may likely do the following.

  • Check the gas cap, especially if the light pops immediately after leaving the fuel station. You may have forgotten to replace or tighten it after filling your gas tank
  • Clean dirty mass air flow sensor
  • Ensure the cooling system is working well
  • Check and replace damaged spark plugs with ones that can withstand heat.
  • Clean or replace clogged air filters
  • Replace or top engine oil with one with high tenacity to withstand heat

Visit a certified auto mechanic.

As your last resort, visit a professional mechanic if the CEL keeps appearing or you’re unsure how to fix these so you don’t cause more damage to your car. In instances where you have the check engine light on but car runs fine, still have it checked.

If the CEL is on, it means there is something that must be fixed. Only a proper diagnosis can help detect the culprit. Moreover, outside from hot weather, several other things can cause the CEL to come on.

Final words

The Check engine light in hot weather can come on for several reasons ranging from a loose fuel cap, to bad spark plugs, etc.

But these are possible guesses. To know why your CEL turns on in a hot climate, scan for error codes with your OBD II scanner or any diagnostic tool.

Clear the codes and see which comes back. But before then, quickly check the gas cap to see if it’s loosened or missing. This is one of the fastest repairs when the check engine light pops, especially if you’re just leaving the gas station.

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Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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