How to Reset Check Engine Light on GMC Sierra?

how to reset check engine light on gmc sierraHave you ever noticed an amber-colored symbol in the shape of an engine on your dashboard that stays on while you are driving? If yes, then you might have a serious problem with your GMC. Although you might not think much about it, especially if there aren’t any other issues, illuminated ‘check engine’ light is a certain sign that your truck has a serious problem.

What does the check engine light do?

Despite its rugged appearance, your GMC is a sophisticated piece of engineering that has a range of sensors that measure temperature, movement of various parts and so on. The computer that controls engine operation uses these values to make it run as efficient as possible. However, if any of these sensors would give readings outside of a predetermined range, the computer will know that something is wrong. To compensate for this unfavorable situation, it will make suitable adjustments to how the engine works. Besides this, it will also trigger that ‘check engine’ light on your dashboard, so you can know that there is some kind of problem.

The major problems with the ‘check engine’ light that stays on is that it doesn’t tell much by itself. This is because many engines or transmission related issues can trigger it. So, when this happens, pay attention to several things. First, see if this warning light is on all the time or it flashes intermittently. While a solid ‘check engine’ light can point to a whole range of issues, one that flashes on and off is a definite sign of an engine misfire. As this is something that can cause irreversible damage to your catalytic converter, pull over at once. Even if the light isn’t flashing, it would be wise to watch for things like loss of power, overheating, unusual sounds and vibrations or anything else that seems out of order. Again, if you notice something like this, continuing your journey might not be a good idea.

How can I find out what triggered the check engine light?

By now, you probably know that the ‘check engine’ light that stays on is not something you should ignore. But, what can you do to make it go away? For starters, you must find out what caused it in the first place. On rare occasions, this will result from a simple system glitch and it will go away on its own. Even if this is the case, checking it out is a good idea, as it may be a sign of an impending problem. And this is where the technology and computers can work in your favor.

All vehicles produced after 1996 come with an On-Board diagnosis system as a standard. This means that every time the ‘check engine’ light goes, it stores a specific information about that event. This goes under the name of the Diagnostic Trouble Code, or DTC for short, and it can reveal a lot about potential problems with your car. Only a decade ago, you would need a dealer specific diagnostic tool to access these codes, making it hard and expensive. Today, there is a whole range of tools that can help you with your troubles.

How can I find out stored DTC codes?

To gain access to stored trouble codes, you will need a scan tool of a sort. The most affordable option is a Bluetooth or Wi-Fi OBD scanner1 that connects to your smartphone. This means you will need to download one of the many applications made just for this job. Despite simplicity, this combo will give you access to trouble codes and also allow you to monitor various live data values. Still, if you want a dedicated device, there is a wide range of hand-held scan tools you can choose from. Similar to the smartphone-scanner combo, it will give you a good insight into the ECU2 of your truck. The downside with both variants is that they can only read engine and transmission trouble codes. This means that systems like anti-lock brakes or airbags are out of your reach.

A step up in the diagnostic department are various manufacturer specific scan tools. Besides reading mandatory engine and transmission codes, these devices will give you insight into engine data logs. Analyzing this information can help you better understand what could cause problems with your engine. These devices will also give you access to other vehicle systems, enabling you to check and clear codes within. Besides this, they can work as a generic scan tool on other vehicle makes. In the end, you can use these tools to reset service intervals for things like oil changes or brake pad renewals.

On the high end of this segment, you will find a range of diagnostic tools. Not only these professional devices can access all vehicle systems and reset service intervals, but they can also deactivate or calibrate various vehicle components. And while features like these make it a powerful tool in the right hands, knowing how to use it requires training and experience. Together with a high price, this makes it less suitable for amateur users.

How can I make the check engine light go away?

Once you have selected a scan tool to your car, it is time for the next step. Find an OBD port in your car, which is usually under the dashboard on the driver’s side. Hook up your scan tool and turn on the ignition. It may take anywhere from several seconds to a minute until it connects to your car is. With a communication set, you can now check diagnostic codes stored with the memory of your car.

Most diagnostic tools or applications will give explanation for each trouble code. However, if that is not the case with your equipment, you can always look it up on the Internet to find out what it means. Still, this is only one half of the job, as you still need to inspect that potentially broken part. For example, stored trouble code may show problems with an oxygen probe or MAF sensor3, while in fact it is down to a loose connector or damaged wiring. So, before buying new parts, make sure there are no such obvious and simple problems.

After repairing or replacing broken parts and components, you still have to delete all stored trouble codes. If everything is right, this will turn off the ‘check engine’ light. To rule out any other issues, take your GMC for a short test drive, as this is the best way to make sure everything is running right.

  1. https://insights.sei.cmu.edu/cert/2016/04/on-board-diagnostics-risks-and-vulnerabilities-of-the-connected-vehicle.html
  2. https://cecas.clemson.edu/cvel/auto/systems/engine_control.html
  3. https://en.wikipedia.org/wiki/Mass_flow_sensor

About the author

Clint Harris

Clint Harris

My name is Clint Harris. I am an automotive fan who is fond of the latest tech- and classic muscle car technology. I launched CarWrenching to share open-minded tips, tutorials, and insight.

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