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By YOUCANIC on Dec 17, 2018

Why is my Cadillac Check Engine Light ON?

Is your Cadillac Check Engine Light ON or Flashing? In this guide, you will learn about common problems that trigger Cadillac check engine light to come on plus step-by-step instructions on how to diagnose Cadillac check engine light yourself.


cadillac check engine light 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 going uphill
  • Engine shakes or excessive vibrations
  • 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 find out 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.

OnStar Subscribers

diagnose cadillac check engine light via onstart

If you are 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 below to read the fault codes yourself. This procedure is very easy and takes less than five minutes. 

How to read Cadillac check engine codes

Reading fault codes to find out why your Cadillac check engine light is ON is the first troubleshooting step. Do not ignore CEL and always pull the fault codes even if your Cadillac runs and drives fine.

What you will need


Reading Cadillac check engine light codes and resetting it once you fix the problem is very easy. Any Cadillac owner can read and clear 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.

Locate OBD-II Port

Locate 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.


Connect Scanner

Plug in your scanner or Bluetooth adapter into the OBD2 port.

Cadillac Check Engine Light ON Troulbeshooting


Turn On Ignition

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

How to diagnose Cadillac check engine light service engine soon ATS, CTS, XTS, CT6, XT5, Escalade, SRX, DTS, STS, BLS, XLR


Turn on 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.

Check Engine Light On Cadillac


Read Codes

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

Clear Codes

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

clear Check Engine Light On Cadillac

Check engine light codes should only be cleared (erased) only after the problem that triggered the light has been fixed. 


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Lori, 2018-04-05

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.

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Mike pal, 2019-03-12

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

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Jef the car guy, 2019-03-12

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

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Jeanette Garrett , 2019-04-10

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

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PamziePam, 2019-04-17

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

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CWenn, 2019-05-28

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

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