Troubleshooting Cadillac Check Engine Light  ATS, CTS, XTS, CT6, XT5, Escalade, SRX, DTS, STS, BLS, XLR

Why is my Cadillac Check Engine Light ON?

Last Updated on Thursday Apr 05, 2018

Does your Cadillac Check Engine Light (CEL) stay on or is flashing? In this guide, you will find instructions on how to diagnose Cadillac check engine light yourself. Cadillac check engine light can turn on for various reasons including something as simple as a loose gas cap. Reading fault codes to find out why your Cadillac check engine light is ON should be the first troubleshooting step. Do not ignore CEL and always pull the fault codes even if your Cadillac runs and drives fine.

diagnose cadillac check engine light via onstartIf 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 you can find a repair shop or auto parts stores that can read the codes for free. Or if you are a DIYer follow the instructions below to read the fault codes yourself. This procedure is very easy and takes less than five minutes. 

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1. Symptoms

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.

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2. What you will need

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3. Instructions

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.

Step 1

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.

Step 2

Cadillac Check Engine Light ON Troulbeshooting

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

Step 3

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

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.

Step 4

Check Engine Light On Cadillac

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

Step 5

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

Step 6

clear Check Engine Light On Cadillac

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.

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Check Engine Light Flashing

If your check engine light is flashing it means that the engine control unit has detected a misfire. You should stop as soon as possible and have your vehicle towed if necessary to prevent further damage to the engine or catalytic converter. 

What this means is that one or more of your cylinders are not working properly. This can be caused by a number of things such as bad spark plug, faulty ignition coil, bad ECU, clogged catalytic converter. 

If your car is flashing the check engine light and you continue to drive, you can damage the engine or the catalytic which can cost anywhere from $800 to $1500 to replace.

Top 10 Causes of Check Engine Light

Here is a list of the most common causes of Check Engine Light. Average costs to repair these problem has been included. Please note that for high-end vehicles the repair cost can be outside of this range. The repair costs shown below are typical prices you will pay at the dealers and auto repair shop. When a DIYer performs these repairs the average cost is significantly lower. 

  1. Oxygen Sensors 
    • Repair Cost: $200-$400
    • Repair Difficulty: Easy 
  2. Catalytic converter
    • Repair Cost: $750-$1500
    • Repair Difficulty: Moderate 
  3. Spark Plugs
    • Repair Cost: $250-$600
    • Repair Difficulty: Easy
  4. Loose Gas Cap
    • Repair Cost: Free - $25
    • Repair Difficulty: Very Easy
  5. Mass Air Flow MAF Sensor
    • Repair Cost: $200-$400
    • Repair Difficulty: Easy
  6. EVAP Purge Control Valve
    • Repair Cost: $120-$400
    • Repair Difficulty: Easy
  7. Ignition Coils
    • Repair Cost: $140-$600
    • Repair Difficulty: Easy
  8. Thermostat
    • Repair Cost: $200-$650
    • Repair Difficulty: Moderate
  9. Camshaft Position Sensor
    • Repair Cost: $150-$400
    • Repair Difficulty: Easy
  10. Fuel Injectors
    • Repair Cost: $350-$650
    • Repair Difficulty: Easy

Important Notes

  1. Clearing the check engine light using a scanner or by disconnecting the car battery does not fix the problem itself. Clearing codes without fixing the problem simply erases the codes from Engine Control Unit memory. Also keep in mind that if your car requires an emissions test soon after you clear the code, you will fail the emissions test. Clearing (CEL) codes also set the emissions readiness indicators to NOT READY. The car will require a few days of driving or a specific drive cycle to test all the emission systems and set them to READY.
  2. We recommend that you get a second opinion from a professional before you replace any parts. Do not replace car parts based on the fault code alone. It is important to consider the symptoms and the code before you come to a conclusion. For example, you may get a code for a bad oxygen sensor. While the oxygen sensor can surely be defective, a code for oxygen sensor can also be triggered by a cut wire, bad connector,  bad catalytic converter etc. Keep in mind that even a mechanic may have a difficult time diagnosing those rare cases. 
  3. If your check engine light turns on while driving continually monitor the engine temperature and oil pressure light. If any of these lights turn on, safely pull over and turn off the engine. 
  4. Do not ignore the Check Engine Light warning. Diagnose your vehicle as soon as possible.
  5. Auto parts stores such as Advance Auto Parts or AutoZone may offer free scanning of the Check Engine Light. 
  6. Check Engine Light (CEL) may also be referred to as Service Engine Soon (SES), malfunction indicator lamp (MIL). 

Frequently Asked Questions

Yes, disconnecting the battery usually clear the ECU codes. By turning the check engine light off this way you will not fix the problem. If you believe the check engine light needs to be off, drive the car for a few days and the CEL will reset itself. The Onboard Diagnostic System in your car continually monitors your vehicle and will turn off the CEL if the problem is solved. If the problem hasn't been resolved, even if you disconnect the battery, the CEL will come back up again which can be as soon as you restart the car or up to a few days.

If check engine light is on, it will not pass emission inspection/smog test. If the light was recently reset with an OBD2 scanner or by disconnecting the battery, you need to drive the car for a couple of days for the systems to be ready for testing.

It could be because you are using an OBD2 scanner that does not support the protocol used in your car. Try a different scanner. Also, there may be an issue communicating with the ECU due to a damaged wire or ECU malfunction.

No. The check engine light is not the reason why the car doesn't start. If the car doesn't start, read the codes and maybe the CEL will give you a code that can help you diagnose the car. Clearing codes will not make your car start.

It may be just bad timing. An oil change is not going to trigger the CEL. Unless MAYBE a sensor got accidentally unplugged, disconnected or damaged during the oil change. Take your car back to the auto repair shop that changed your oil and have them diagnose the problem.

No, the CEL should not turn on after routine maintenance. If you modified your engine, transmission, exhaust, intake, fuel system or other systems it can affect engine and emission control system, causing check engine or service engine soon light to come on. CEL should not come on if you changed tires or tire size.

Drive the car for a couple of days and allow the ECU to reset itself. If the CEL still remains on, read codes.

The check engine light is trying to tell you that there is a problem with your engine. It could be low coolant, stuck thermostat, transmission not shifting. Figure out why your car is overheating first and address that problem. DO NOT CONTINUE TO DRIVE IF YOUR CAR OVERHEATS.


Posted by Lori on Apr 5, 2018 @ 12:04 pm