Cadillac Check Engine Light Stays On

Cadillac Check Engine Light Stays On

Is your Cadillac Check Engine Light ON or Flashing? Learn how to read the codes and discover why your Cadillac check engine light comes on.

There are over 500 different fault codes that can trigger the check engine light on a Cadillac. You will need to read codes to find out why the check engine light on your Cadillac is on.


Symptoms of a check engine light can vary depending on the fault code that triggered the light. Possible symptoms include:

  • Poor throttle response
  • A decrease in fuel economy
  • Engine misfire
  • Difficult to accelerate or go uphill
  • Engine shakes or excessive vibrations
  • The car won’t stay running.

The check engine light may be on, with no symptoms. Even if there are no symptoms, it is important to read the fault codes to determine why CEL is on.

Common Causes

Cadillac check engine light can turn on for various reasons, including something as simple as a loose gas cap.

  • Loose gas cap
  • Faulty MAF sensor
  • Oxygen sensor
  • Catalytic converter
  • EVAP leak
  • Vacuum leak
  • EGR Valve

It isn’t easy to know the cause of the check engine light without reading the codes.

How to read Cadillac codes

The following steps provide information on how to read Cadillac fault codes from the Engine Control Unit (ECU).

What you will need


The YOUCANIC Full System Scanner can read and clear fault codes through every vehicle’s control module.



  1. Locate the OBD-2 port under the dashboard of your Cadillac on the driver’s side. This is a 16-pin port, and all 1996 and newer Cadillac vehicles have this port.
  2. Connect Scanner. Plugin your scanner or Bluetooth adapter into the OBD2 port. connect obd2 scanner to obd2 port

  3. Turn ignition ON, key in position II. All Cadillac dashboard lights will turn on but do not start the engine. If your Cadillac has a Start/Stop button, you must press the START button without pressing the brakes. check engine light on dashboard

  4. Turn on the scanner. Allow your OBD2 scanner to turn on and connect to your Cadillac Engine Control Unit (ECU). This step can take up to one minute. read scanner codes

    PXL 20220312 003004456

  5. Read Codes. Read Cadillac check engine light codes from the Engine Control Unit (ECU).

  6. Clear Codes. Once you have read the codes and fixed the underlying problem, you can come back to clear Cadillac CEL codes. Go to the Erase Codes menu. Select YES to clear the Cadillac check engine light.

    clear codes on scanner
    003033601 (1)

  7. Check engine light codes should only be cleared (erased) after the problem that triggered the light has been fixed.
Reading Cadillac check engine light codes and resetting it once you fix the problem is straightforward. Any Cadillac owner can read and clear the Cadillac check engine light at home.
This procedure works on Cadillac ATS, CTS, XTS, CT6, XT5, Escalade, SRX, DTS, STS, BLS, XLR, and other models.

OnStar Subscribers

diagnose cadillac check engine light via onstart

If subscribed to OnStar, press the button to connect to an Advisor. They can run a diagnostic check and retrieve the trouble code(s) from the Engine Control Unit (ECU).

If you are not subscribed to OnStar, follow the instructions to read the fault codes yourself. This procedure is effortless and takes less than five minutes.

We hope you find the Cadillac Check Engine Light Stays On guide helpful. Check these troubleshooting and repair guides for more help on your Cadillac.


  • Rushit Hila • ASE Certified

    Rushit Hila, an ASE-certified engineer (G1 Automotive Maintenance and Repair), brings over two decades of hands-on experience in the automotive world to his writing. With a strong educational background, including a Master of Science in Engineering and a Bachelor of Science in Engineering, he has honed his skills and expertise through years of practical work. As a respected authority in the field, Mr. Hila is dedicated to offering insightful and valuable content that resonates with both vehicle owners and mechanics.

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  1. Anonymous says:

    I have a 2007 escalade and I have few warning lights on. The scanner pointed me to a couple of the problems but on a couple others it said it cant connect to the ecu. Why is it reading some problems and not others?

  2. Anonymous says:

    2015 Cadillac SRX. I changed my low beam head light bulbs to LED bulbs trying to get more light. Now the check engine light is on. Is this related?

  3. Anonymous says:

    My 2005 Cadillac cts chef engine light came on after my car was shut off and stays on and drains my new battery. What could be causing the issue please help. This is one among a few issues I’ve been having. Really love this car.

  4. Anonymous says:

    O’Reilly will check the codes for free. They have always been helpful.

  5. Anonymous says:

    How much did you Pay at O’Reilly to have your car checked???

  6. Anonymous says:

    Hello my name is Jeanette I have a 2007 Cadillac STS my engine light on I went to O’Reilly to get it checked and they gave me codes I do not understand p0455 p0301 p0300

  7. Anonymous says:

    No the check engine light should not come on because you haven’t changed the oil. Hope this helps.

  8. Anonymous says:

    Can a past due on you’re oil change or due on the date cause check engine light to come on a ats 2014

  9. Anonymous says:

    My car has less then 96k miles and the check engine light came on and it showed codes p0017 & p0008. Gm issues a service bullentin (11340) and later extended it to include the 2009 Cts ( 11340c) for premature timing chain wear. Even though my cars make, model and year is listed under sb 11340c, when you call gm, they say my VIN isn’t included. Obviously, my car which year is listed should be covered and gm should repair under this sb. It is the exact same issue the sb was issued for. Gm is scamming their customers and there needs to be a recall for this issue. I read thousands of people complaining about the same issue, and all that needs to happen is for the htsa to require all the 2009 Cts that had to have this issues repaired at their own expense while gm reaps the rewards of each car that they have a known engineering issue.