Can OnStar Diagnose Check Engine Light? [25 Causes]

Check Engine Light

Your vehicle’s “Check Engine” light can be a little scary. The yellow light often warns about the engine’s health and sometimes indicates serious engine trouble ahead. Having an OnStar module in your car can diagnose many of your vehicle issues, but can OnStar diagnose check engine light?

OnStar vehicle diagnostics can help identify issues with your car and provide recommendations for how to fix them. Keep reading to learn more about the causes and OnStar diagnostics of the Check Engine light.

Can OnStar diagnose check engine light?

Yes, OnStar provides a detailed diagnosis of check engine lights in its On-Demand Diagnostics check services. You only need to contact OnStar Advisor or by pressing the blue OnStar button on your device. To avail the service, you need to enroll in Vehicle Diagnostics.

They OnStar will remotely diagnose your engine status and identify the diagnostic alerts with the codes.

Once the diagnosing process is complete, OnStar advisors will provide you with a list of diagnostic codes, recommendations on fixing the issue, and step-by-step instructions. The advisor will also help you access repair shops and nearby dealers to fix the issue.

Can OnStar Diagnose Check Engine Light

What is OnStar On Demand Diagnostics Check?

OnStar On-Demand Diagnostics Check is a convenient way to stay up-to-date with your vehicle’s health.

This service allows OnStar advisors to connect directly to your car’s onboard diagnostic system and provide a comprehensive overview of its condition.

From engine performance issues to tire pressure monitoring and oil life levels, the OnStar On-Demand Diagnostics Check can quickly identify any potential problems that might need attention.

With this data in hand, you’ll be able to make informed decisions about how best to maintain your vehicle.

OnStar On Demand Diagnostics Check

How does OnStar vehicle diagnostics check engine lights?

OnStar diagnostics scans your car computer in real-time to detect any errors or issues that could be causing your engine yellow light to turn on.

The diagnostic scan includes a detailed vehicle health update of all components within your car engine and transmission.

OnStar then provides a diagnostic code of the errors and guides you with the appropriate recommendations or solutions to properly diagnose and fix the issue.

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What Causes Check Engine Lights?

  1. Loose or Faulty Gas Cap
  2. O2 Sensor Failure
  3. Mass Airflow Sensor (MAF) Failure
  4. Vacuum Leak
  5. Catalytic Converter Failure
  6. Spark Plug or Ignition Coil Issues
  7. Evaporative Emission Control System (EVAP) Failure
  8. Exhaust Gas Recirculation (EGR) Valve Stuck Closed
  9. Engine Misfire
  10. Low Coolant Level
  11. Low Oil Level
  12. Faulty Throttle Position Sensor (TPS)
  13. Exhaust Leak
  14. MAP Sensor Failure
  15. Faulty Oxygen Sensor Heater
  16. Engine Temperature Too High/Low
  17. Faulty Camshaft or Crankshaft Sensor
  18. Faulty Fuel Injectors
  19. Leaking Intake Manifold Gasket
  20. Faulty Fuel Pressure Regulator
  21. Blocked EGR Valve
  22. Faulty Ignition Switch:
  23. Incorrect Fuel Octane Level:
  24. Dirty Air Filter:
  25. Faulty Throttle Body

How do I get OnStar to run a diagnostic test?

To run the Onstar Diagnostic test:

  1. Call OnStar customer support at
  2. Push your OnStar blue button to access the advisor

What are the OnStar diagnostic Alerts?

OnStar Diagnostic Alerts allow customers to stay informed of their vehicle’s performance and provide early warning for potential issues. These alerts include:

  • Excessive Oil Consumption
  • Extreme Overheating
  • Airbag system
  • Low Coolant Warning
  • Low Tire Pressure Detection
  • Antilock brake system
  • Engine and transmission system
  • Battery Voltage Monitoring
  • High or Low Oil Level Detection
  • Malfunction Indicator Light Detection
  • Exhaust Gas Recirculation (EGR) Fault
  • Evaporative System Monitoring
  • Catalytic Converter Efficiency Loss Detection.
  • StabiliTrak® stability control system


Do I have to pay for OnStar diagnostics?

You don’t have to pay extra for OnStar Vehicle Diagnostics if you have an active subscription to OnStar services.

However, if you have no active plan or have expired subscription, you will need to pay for the plan’s activation to avail of OnStar services.

How long is it OK to drive with check engine light on?

It is not recommended to drive when your check engine light is on. Ensure your safety first, and never ignore the light for long. If you decide to drive, make sure to down your door glasses for smooth oxygen exchange.

The Check light of the engine indicates a malfunction in the vehicle, and you should take it to an authorized service center immediately. If you have to drive, make sure you don’t exceed the speed limit and keep an eye out for any more warning signs that could arise due to the malfunctioning.

Is OnStar diagnostics free?

No, OnStar Diagnostics is not free. Prices vary depending on the length of the subscription period and the level of service chosen. In addition, there may be additional fees for specific services or features. For more pricing information, please get in touch with the OnStar call center.


OnStar can greatly help diagnose your check engine light and provide you with the necessary recommendations on how to fix the issues. It is important to note that OnStar cannot fix the issue.

It is only there to diagnose and provide recommendations on what must be done to fix the issue.

It is essential to take care of any engine light problems as soon as possible to ensure your safety and that your car runs properly and efficiently.

If you are an OnStar customer and need any help with engine light issues, take advantage of the OnStar service.

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