No one likes it when their car’s check engine light illuminates.
The check engine light often indicates an issue with the car engine, either minor, like the faulty fitting of the oil cap, a faulty cap, or a serious problem like a misfitting engine.
Regardless of the case, you should consider visiting your car dealership or your mechanic to determine what is causing the light and how to fix it.
The malfunction indicator lamp (MIL), or in layman’s language, the check engine light, is a signal presented on the Engine Control Module (ECM) to indicate that something is wrong.
But what could be the cause of check engine light after oil change?
Common causes of check engine light after changing oil are improper fitting of the oil cap or dipstick. You can quickly fix this issue by placing the oil cap correctly or fitting the dipstick. After these adjustments, you have to give the engine some minutes to restart so that the light does not come on again.
What Causes Check Engine Light After an Oil Change
There is never a time that is considered good for a car breakdown. Therefore, a check engine light is, at all times alarming. That is the reason why you should read this whole article on the causes of check engine light and how to fix them.
1. Dipstick Isn’t Fully Seated
A dipstick is a tool used to measure the amount of engine oil in a car. When checking car oil, you usually remove, clean, fit, and reseat the dipstick a couple of times to check the oil level.
The dipstick is fitted in a dipstick tube with the O-ring that creates an airtight seal to prevent oil leakages when the engine starts.
If the dipstick is not fitted correctly, it creates space for unmetered air to enter the engine, which, as I stated earlier, will illuminate the check engine light.
A point worth noting is that most mechanics are not paid much money to conduct an oil-change job; therefore, most of them rush through the process.
It is crucial to ensure that the mechanics fit the dipsticks properly to avoid the check engine light.
The solution to this problem is easy to open your vehicle’s hood, locate the dipstick, and set it correctly.
2. Backways Fitted Oil Cap
As much as it sounds like something minor, how the oil cap is fitted potentially causes a check engine light. This becomes evident once you understand how everything works.
In simple terms, your engine requires specified fractions of oxygen and gas to operate at optimum. These fractions are called the Air Fuel Ratio, 14.7:1, for air and fuel, respectively.
The onboard computer on your car serves the function of balancing the ratio.
The Engine Control Module (ECM) manages the ratio by measuring the amount of air entering via a sensor known as the Mass Airflow Sensor (MAF).
The ECM does a simple calculation based on the amount of air entering the engine and calculates the amount of gas required to achieve optimum function.
The main problem occurs when additional oxygen leaks into the engine without the ECM noticing. This explains exactly what happens when the oil cap is fitted incorrectly.
When the cap is fitted backways, it leaves a space that allows for the entry of extra air. Improper fitting causes a vacuum leak that causes the engine to run lean.
Lean in this context means having too much air than the engine requires to run.
The ECM, however, is quick to notice such variations, and it utilizes a probe in the exhaust to calculate how well the fuel that it is adding is being used.
The sensor in the exhaust is called the oxygen sensor.
The ECM has a specific range of measurements that it can accept from the oxygen sensor as long as fuel is added to the engine.
If oxygen reading goes beyond the ECM standards, it is noted and indicated by the check engine light.
How to fix the problem
As easy as it may seem, the solution for this issue is removing the oil cap and fitting it correctly. For most cars, the proper way means that the oil cap faces you and not the other way.
Why should companies develop caps that can be fitted backways? It has worked for several brands, and the design is most common in premium vehicle brands.
3. Too Much Oil
Having too much oil is another major cause of the engine check light. Too much oil can cause the engine to feel sluggish; sometimes, it even causes smoking at the tailpipe.
It can cause minor effects such as misfiring and have consequences as serious as the car not starting up.
This problem can be avoided by checking the oil level following the steps below:
- Park your car on level ground.
- Give the engine some minutes to cool before checking.
- Pop the hood of the vehicle.
- Locate your dipstick.
- Clean the dipstick with a clean cloth before using it.
- Refit the dipstick in the tank and remove it to read the measurement
The dipstick has an upper mark that you will check; some are indicated as Full, “F,” or maximum “Max.” Either way, you will know how much oil is in your tank.
The bottom of the dipstick is marked Low, or Minimum “Min” to indicate the least amount of oil that your car can utilize.
An oil level indicated on the middle or hatched part of the dipstick shows the acceptable levels of oil, which are neither too high nor too low.
Ways of Getting Rid of Excess Oil
You can remove the excess oil from the engine by taking your car back to the garage, where the oil was changed. You can use the dipstick siphon pump to siphon extra oil.
You can achieve this by using a siphoning tool, usually inexpensive and easy to use.
4. Inadequate Oil Pressure
As a car owner, changing oil is necessary after the recommended oil mileage. It, however, should not lead to the check engine light.
This process also resets the oil pressure gauge resulting from oil draining from your car’s engine.
As easy as it sounds, changing the oil and putting on a new filter does not guarantee enough time to achieve a correct reading.
Therefore, the car ECM turns on the check engine light, “thinking” that the oil level is low.
The solution to this problem is allowing the engine some minutes so that the oil flows, and once the ECM registers, the light will automatically turn off.
5. Faulty Oxygen Sensor
The oxygen sensor in your car is the part that determines the amount of air that the vehicle is using.
All cars have two four oxygen sensors, and malfunctions in any of them can trigger the illumination of the check engine light.
A faulty oxygen sensor can decrease the efficiency of the vehicle’s fuel and increase the number of emissions produced during a ride.
A faulty oxygen sensor can destroy the catalytic converter.
Replacing the oxygen sensors in good time can save you a lot of money because you will avoid the expenses of replacing a catalytic converter.
Other Causes of Check Engine Light
When you do not know what is causing the check engine light, you can use a code reader. They are inexpensive and can be used to detect the causes of engine malfunctions.
If you cannot access a code reader, the following are some other causes of the check engine light.
Oil Sensor Did not Reset Properly
How to Reset the Check Engine Light After an Oil Change
- When the check engine light comes on, your car may allow a method to turn it off easily.
- Here are the steps you can follow;
- Insert and turn the key on ignition; do not turn on the engine, but allow all the indicator lights to come on.
- Identify the “reset” stick. It is usually located between the tachometer and speedometer.
- Press on the reset stick continuously until the check engine light blinks. The blinking indicates a successful reset.
- Remove the key from the ignition and re-insert it to start your vehicle. If your car does not have any other issues, this method is enough to turn off the check engine light.
Cars use oil that differs in viscosity, grade, or weight. For example, you can mistake 5w-40 oil for 0w-40 oil.
Using too viscous oil will not provide adequate lubrication, which will affect heat transfer. This can result to oil overheating and eventually check engine light.
If this happens, you should drain the oil, replace the oil filter and use the right oil grade.
Faulty Mass Airflow Sensor
The Mass Airflow Sensor(MAS) controls the amount of air that enters the engine. It helps the ECM determine the amount of fuel it needs to inject to achieve an effective burn.
A faulty MAS causes increased emissions because unburned fuel gets combusted at the exhaust.
What causes the MAS to malfunction?
It is due to a blocked air filter usually caused by insufficient cleaning. Old and faulty filters need replacement.
Faulty Engine Coolant Thermostat
The engine coolant thermostat manages the flow of coolant in the engine. Without the coolant, the engine will overheat. If this happens regularly, the check engine light will come on.
A faulty thermostat can also make the coolant heat considerably, which can cause a radiator leak. If it leaks, the engine will overheat, thus illuminating the check engine light.
Exhaust Gas Recirculation
The exhaust gas recirculation (EGR) is a valve that minimizes the ratio of toxic nitrogen oxide released from the exhaust. Current models of vehicles have computerized EGR valves that automatically open and close.
If the airflow seems off, the check engine light will come on.
Excessive Carbon Buildup: Excessive carbon buildup causes the EGR valves to stick, thus, interfering with their function. You can identify this problem if your car “hiccups” when idling.
You can solve this problem by visiting the mechanic and asking them to clean the EGR valve.
Faulty Spark Plugs and Ignition Coils
The ignition coil provides a push to spark the plugs, causing gas ignition in the tanks. Faulty ignition coils are risky because they can cause misfires; thus, the check engine light will come on.
On the other hand, faulty spark plugs mess up car acceleration and make it sluggish.
Note that this affects only gasoline-powered vehicles because diesel-powered vehicles are not built with plugs and ignition coils.
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On Check Engine Light After Oil Change
You may not know what is causing the check engine light to come on if you do not get it checked by a professional. It may indicate something harmless or critical, and you should not ignore it.
Ensure that the oil cap is fitted correctly and tightly, as this is one of the main reasons the engine check light is illuminated.
Hi I’m Marshall based in 1478 Doctors Drive Santa Monica, CA. I’m your DIY Car Repairman with more than 5 years experience in automobile repair, a skill I learned from my old man.
I started this blog to share my experience on both simple and technical aspects of your car.