Are you seeing the dreaded “check engine” light illuminate on your GMC dashboard? This warning light comes on when the onboard diagnostic system detects a problem with your engine. Here’s what may be wrong with your car.
A GMC check engine light could be triggered by something as simple as needing to tighten your gas cap. Or, the warning light can indicate a more serious problem, such as an issue with an oxygen sensor, bad mass airflow sensor, or defective ignition coil.
While it’s true that there are plenty of potential issues that could be causing your check engine light to appear, most don’t necessarily require immediate action.
Truthfully, it doesn’t matter if you drive a Nissan, Buick, GMC, Hyundai, Mazda, or Ford – eventually you see the check engine warning light up.
So how do you tell if this warning sign is truly something to worry about?
Simply put, there are two check engine light behaviors – either flashing or steady illumination.
If the light is flashing, this typically indicates a serious problem that requires immediate attention. It’s recommended that you stop driving your GMC vehicle immediately. Have a qualified mechanic run a diagnosis scan to find the problem.
However, if the light is a steady illumination, it may still indicate a problem, but not as urgent. And in most cases, you can continue to drive the vehicle without further damaging your GMC vehicle.
But, it’s still important to have the vehicle diagnosed as soon as possible, as these problems can turn into bigger headaches if not dealt with swiftly.
Thankfully, this guide will provide some clarity around the causes and implications of a GMC check engine light coming on.
We’ll tell you what to do first and answer questions like whether it’s safe to continue driving when the light is illuminated.
So if your check engine light has just come on and you need answers, stick around!
What Does The GMC Check Engine Light Mean?
Simple put, the “check engine” light on a GMC vehicle is like your car’s way of shouting out for help. It could be something as small as a loose gas cap, or it might mean that one of the sensors isn’t functioning properly.
Don’t ignoring this warning sign, as it may lead to worse problems down the road. In fact, you may begin to notice decreased fuel efficiency, increased emissions, and possibly the vehicle even stalling or breaking down.
Of course, the behavior of the dreaded check engine light can give you some sense of how urgent the matter is.
For instance, A steady, solid illuminated light indicates a minor mechanical problem. Whereas a flashing check engine warning light means a serious mechanical problem.
However, regardless of the a steady or flashing light – when that light turns on – take action!
What’s The Easiest Way to Find Out Why Check Engine Light is on?
The easiest way to identify what’s wrong with your car is by scanning the error codes. If you have an OBDII diagnostic scanner, you can connect it to the car to see a displayed error code that’s causing the check engine light to appear.
No diagnostic scanner of your own? No problem! Just head down to the local auto parts store and get those trouble codes read out for free.
What Could Cause My GMC Check Engine Light to Come On?
Truth is, there are a handful of issues that can cause the check engine warning light to come on. Because the OBD-II system in your GMC is constantly monitoring and measuring various engine and vehicle parameters.
And if just one of these sensors is detected as malfunctioning, it will trigger the warning light.
As you can imagine, these sensors are generally pretty accurate. So when that check engine warning appears, their is a mechanical issue that needs attention.
Below is a list of some of the top causes for that pesky GMC warning light.
Bad Mass Airflow Sensor
The mass airflow sensor (MAF) is responsible for determining airflow into the engine and sending that information to the control module. When it’s not working properly, the air-fuel ratio can be disrupted, causing a host of problems with the engine.
Cleaning or replacing the MAF should fix the issue.
Defective Ignition Coil
The ignition coil is responsible for converting the voltage into the active spark that ignites in the combustion chamber. When the coil is malfunctioning or misfiring, it can cause problems with the engine. These problems commonly include misfiring, stalling, backfiring, and bad fuel economy.
Find and replace the defective coil to fix the issue.
Malfunctioning Oxygen Sensor
The oxygen sensor records the amount of oxygen in the engine and sends that information to the powertrain control module. This determines the real time air-fuel ratio.
When the sensor malfunctions, your car will likely have poor fuel economy, lack of power, and additional exhaust fumes.
Replace the defective Oxygen Sensor to fix the issue.
Loose or Defective Gas Cap
Simple as it may seem, a loose or faulty gas cap can cause the check engine light to come on. Make sure your cap is on tightly, and if it appears chipped or damaged, replace it.
Is it Safe to Drive With My GMC Check Engine Light On?
It depends, but generally it’s not recommended you drive your GMC with a check engine light is on.
While true in some circumstances, the check engine light may illuminate due to minor issues, such as a loose gas cap or faulty sensor. So in this case, the check engine light will be a solid or steady illumination. Then it’s generally okay to drive the vehicle before getting the car looked at by a mechanic.
However, other times it can be an indication of a more serious issue – such as engine misfire or transmission problems. This is a more serious problem, and the car will let you know by blinking or flashing the check engine light.
If you have a flashing or blinking check engine light, continuing to drive the GMC can potentially cause further damage, and may result in costly repairs.
And if you GMC is going in for emissions inspection, a lit check engine light always results in an automatic failure of the test.
How Much Does it Cost to Have My GMC Check Engine Light Diagnosed?
The cost to diagnose a GMC check engine light can vary depending on several factors. Factors such as dealership’s pricing, location, and the severity of the issue.
With that said, expect to pay an average of $100 to $150 for a diagnostic check at a GMC dealership, or $50 to $100 for an independent mechanic.
However, keep in mind that the cost of repairs, if needed, is not included in the diagnostic fee.
If you’re concerned about the cost, consider taking your GMC to an independent mechanic who specializes in GMC vehicles.
Because they may be able to diagnose and fix the issue at a much lower cost than a dealership. However, they may not be able to provide a warranty for the work performed. So just keep that in mind.
Final Thoughts: GMC Check Engine Light
Diagnosing a check engine light on your GMC vehicle can be intimidating. It’s true that it could indicate a serious problem, or something as simple as a loose gas cap.
If your warning light appears, take the time to uncover what’s causing it so you aren’t running around in circles trying to pinpoint where the issue lies. Of course, you can also take your car to a mechanic and have them identify the issue for you.
Finally, make sure to double check any solutions recommended by a mechanic before having work done on the car and review warranty information.
Managing Editor
Christopher is an automotive technical writer. When he’s not at the local autocross event, he can often be found working on one of his cars. Specializes in automotive class action law, industry trends, and automotive maintenance. Email me direct, or learn more about us
