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Check Engine Light is ON After Oil Change! Why?


Why would a Check Engine light come up after the oil change? Check Engine light will come ON briefly after the oil change because it needs a few minutes to circulate through your engine and all the necessary passages to build pressure. After the oil sensor recognizes the oil pressure, it will go off by itself. 

Check Engine could shortly come up at every start after the oil change and will go away after about 3 engine starts cycles. Resetting the Check Engine light by yourself is possible and how to do it is mentioned below, ONLY make sure it came up RIGHT AFTER the oil change, NOT before or way after!

If you had the Check Engine light lit BEFORE your oil change, changing oil WILL NOT solve your problem!

On the other hand, if your light comes ON several days AFTER the oil change, it could mean something more serious. Your mechanic needs to check fault codes with the OBD II scanner and reset the Check Engine light once the problem is fixed.

Auto Parts stores could also hook up a scanner and check the codes for you. The diagnostic port is located under the dashboard and you can get this cool gadget yourself to check the codes!

This particular OBD II scanner from Blue Driver (paid link) gets connected to your smartphone and helps you read codes:

If after several days from the oil change, your Check Engine light comes ON, it’s either because:

  • Something was done improperly during an oil change
  • Something is happening to your vehicle UNRELATED to the oil change

First of all, let’s take a look at the light, is it flashing or is it solid?

Solid light is there to notify you of emissions control system problems. The Flashing Check Engine light notifies your catalytic converter is getting damaged due to misfire and your car should be stopped and taken to the service center right away!

Other reasons for your light coming up a couple of days (NOT immediately) after the oil change are:

  1. Wrong oil grade. You need to use the oil grade that your manufacturer specifies, otherwise, you are risking drastically increasing the temperature of your engine, and yes, the Check Engine light will come ON!
  2. Your oil is leaking. If you can, check for oil leaks yourself or have the mechanic inspect your oil lines. There could be a blockage in oil transferring lines or oil pumps. Check if your oil cap is properly tightened.
  3. Internal oil leak. If your oil is leaking internally in the oil-sending unit, your Check Engine light could be triggered as well. This is a quite serious problem and should be addressed ASAP.
  4. Your oil filter wasn’t changed. A new filter should be installed with every oil change and if it’s not, it could block new oil coming through. Overheating of your engine could follow and Check Engine light would notify you of a problem as well.
  5. Oxygen sensor problem. If your oxygen sensor is faulty and not giving your onboard computer the correct information, then a Check Engine could come up. In this case, you will need to replace this sensor.

Am I using the wrong type of oil?

Now, let’s get back to the motor oil. SAE (the Society of Automotive Engineers) established a numerical code for grading motor oils.

Since the viscosity of oil changes with temperature, it has two numbers, one at the start (W-Winter) and one at normal engine operating temperature. It goes as follows:

  • 0W-20. 0 viscosity at the start and 20 at normal operating temperature.
  • 0W-30. 0 viscosity at the start and 30 at normal operating temperature
  • 0W-40. 0 viscosity at the start and 40 at normal operating temperature.
  • 5W-30. 5 viscosity at the start and 30 at normal operating temperature.
  • 5W-40. 5 viscosity at the start and 40 at normal operating temperature.
  • 10W-40. 10 viscosity at the start and 40 at normal operating temperature.

The lower the number, the thinner the oil, and the correct type of oil MUST be selected according to your manufacturer’s specifications. Thicker oil offers a better seal and better lubrication of your motor than thinner oil.

It also increases the life of your car engine due to its superior thermal stability. Having said that, using the wrong type of oil in your vehicle is not recommended because:

  1. If your oil is too thick, you may experience poor fuel efficiency and your gas mileage will go down.
  2. If your oil is too thin, your engine may start overheating since the components will NOT be lubricated well enough.

If oil viscosity is NOT suitable for your car or is thinner than your manufacturer recommends, your engine will most likely get damaged soon. How to make sure you are using the correct type of oil?

Verify what type of engine oil your mechanic used and compare the number with manufacturers recommendations

Wrong types of oil could also create leaks and the level of the oil will dip. This applies more to older cars.

Why check engine light ON after oil change?

Check Engine light could come up after the oil change also because of the following:

1. The oil cap is NOT fitted in the correct way

Sounds silly? It’s not! If the oil cap is fitted backward, it will not seal properly and therefore allow more air than necessary inside the engine. All you have to do is remorse the cap and put it back correctly (writing should face you).

2. The dipstick is not fully seated

This is again a simple fix and all you have to do is seat your dipstick fully. The reason for this being a problem is very similar to the above situation and if unmetered air sneaks into your engine, the Check Engine light will come ON. The dipstick needs to fit properly into its tube for the O-ring to seal the air vacuum.

3. Double gasket mistake

This happens if the new filter is installed on top of an old seal. This situation would allow a severe oil leak that would turn your Check Engine light ON. Your oil could blow as you start the car or when you go down the road, so you need this to be fixed ASAP.

4. The oil reservoir is NOT as full as it should be

Yes, quick oil change places sometimes forget to add the full amount of oil. The low oil level will cause a variable valve timing code and your Check Engine light will come ON. Just add some fresh oil to the proper levels and your problem should be solved.

5. The drain plug is NOT properly tightened

If your drain plug is NOT tightened well enough, your oil will drain out as you drive. Low oil levels along with performance problems could cause the Check Engine light to come ON.

Why does this happen? Many times oil change is a rushed procedure since it is not a very profitable one. You can examine oil lines yourself to see if anything is leaking or disconnected and then take it to the mechanic if a problem is found.

Can oil change cause check engine light?

By itself, the oil change process should NOT trigger the Check Engine light. Unintentional disturbance of a sensor or knocking wiring loose could also create Check Engine light problems.

Sometimes, sensors INTENTIONALLY get disconnected by desperate mechanics that need more work. Definitely, NOT everyone is like that, so if you got a good and honest mechanic, hold on to him!

If there was something else done in the air filter area, maybe the mechanic did not put everything back correctly or dislodged a vacuum hose. Here is another reason why the Check Engine light could be triggered after the oil change and air filter change:

How to turn off check engine light after oil change?

Did you happen to refuel your engine between now and your oil change service? If so, check your gas cap. The check Engine light could be triggered by a poorly tightened fuel filler cap and that should turn the Check Engine light OFF.

You are NOT supposed to have a Check Engine light after the oil change because your mechanic was supposed to turn it OFF.

If you are driving away from the service station with Check Engine light ON, go right back and ask them to reset it!

It is also possible that it came ON after the oil change took place, so if you are 100% that nothing else is wrong with your car, then watch this video on how to reset and turn OFF your Check Engine light manually:

Hope this helps and here is a map of the nearest automotive repair shop:

Attention! This article is for informational purposes ONLY and is NOT a replacement for professional advice! ALWAYS consult your local specialist for an appropriate solution to your problem. All statements, prices, contact information, recommendations, and reviews contained herein came from sources that we believe to be reliable, but the accuracy or completeness thereof is not guaranteed. Please contact the service provider for complete details and updates.

1 Comment

  1. Willie Austin

    Well, from what I know, overfilling the engine oil can also cause the CEL light on. So, if it happens, remove excess oil below the proper level.

    And the bad o2 sensor won’t make CEL on after an oil change, but the oil pressure sensor will.

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