Resetting the check engine light on your 2017 GMC Sierra is simple once you understand the root cause and proper method. This guide walks you through safe, effective steps—from diagnosing the issue to clearing the code—so you can drive with confidence.
Key Takeaways
- Diagnose the problem first: Never reset the light without fixing the underlying issue—otherwise, it will return.
- Use an OBD2 scanner for accuracy: This tool reads and clears trouble codes safely and provides detailed diagnostics.
- Disconnecting the battery works—but has risks: It can reset the light but may also erase radio settings, adaptive transmission data, and more.
- Drive cycles matter: After resetting, your truck needs a proper drive cycle to verify the fix and prevent the light from coming back.
- Check gas cap first: A loose or damaged gas cap is a common cause of the check engine light on GMC Sierras.
- Professional help is wise for complex issues: If the light returns or you’re unsure, consult a certified mechanic.
- Regular maintenance prevents future warnings: Keep up with oil changes, air filters, and spark plugs to avoid recurring problems.
How to Reset Check Engine Light on 2017 GMC Sierra
Seeing the check engine light illuminate on your 2017 GMC Sierra’s dashboard can be stressful. It’s a warning sign from your truck’s onboard computer—also known as the powertrain control module (PCM)—that something needs attention. But don’t panic. In many cases, the issue is minor and easily fixable. The good news? You can reset the check engine light yourself, often without visiting a mechanic.
This comprehensive guide will walk you through everything you need to know about resetting the check engine light on your 2017 GMC Sierra. You’ll learn why the light comes on, how to diagnose the problem, and the safest and most effective ways to clear it. Whether you’re a DIY enthusiast or just want to save a trip to the shop, this step-by-step tutorial will help you take control of your vehicle’s health.
Why Does the Check Engine Light Come On?
Before you reset the light, it’s crucial to understand why it turned on in the first place. The check engine light—also called the malfunction indicator lamp (MIL)—activates when the PCM detects a problem with the engine, emissions system, or related components. These issues can range from minor to serious.
Common causes include:
- A loose or faulty gas cap
- Faulty oxygen (O2) sensor
- Misfiring spark plugs or ignition coils
- Dirty or failing mass airflow (MAF) sensor
- Catalytic converter issues
- Evaporative emissions system leaks
- Exhaust gas recirculation (EGR) valve problems
On the 2017 GMC Sierra, the most frequent culprit is a loose gas cap. After fueling, if the cap isn’t tightened properly, it can trigger the light within a few drive cycles. Other common issues include O2 sensor failures due to age or contamination, especially in high-mileage trucks.
Ignoring the light can lead to reduced fuel efficiency, increased emissions, and even engine damage over time. That’s why it’s important to address the root cause before resetting the light. Simply clearing the code without fixing the problem is like turning off a smoke alarm while the fire still burns.
Tools You’ll Need
To reset the check engine light on your 2017 GMC Sierra, you’ll need a few basic tools. Most are affordable and easy to find.
OBD2 Scanner
The best and most reliable way to reset the light is with an OBD2 (On-Board Diagnostics II) scanner. This handheld device plugs into your truck’s OBD2 port—usually located under the dashboard, near the steering column—and communicates with the PCM. It reads diagnostic trouble codes (DTCs), tells you what’s wrong, and allows you to clear the codes safely.
You can buy a basic OBD2 scanner for under $30, or invest in a more advanced model with live data and Bluetooth connectivity. Popular brands include Innova, BlueDriver, and FIXD. Many auto parts stores also offer free code reading if you don’t want to purchase a scanner.
Basic Hand Tools
If you’re planning to fix the issue yourself—like replacing a gas cap or air filter—you may need a few hand tools. A socket wrench, screwdriver, and pliers are usually sufficient for most under-hood tasks on the 2017 Sierra.
Multimeter (Optional)
For advanced diagnostics—such as testing sensor voltages or checking for electrical continuity—a multimeter can be helpful. However, it’s not required for basic reset procedures.
Step 1: Diagnose the Problem
Never reset the check engine light without first identifying and fixing the issue. Here’s how to do it properly.
Check the Gas Cap
Start with the simplest fix. Open the fuel door and inspect the gas cap. Is it cracked, worn, or missing the rubber seal? If so, replace it. Even if it looks fine, try removing it, cleaning the threads, and reinstalling it tightly. A loose cap can cause a pressure leak in the fuel system, triggering the light.
After tightening or replacing the cap, drive your Sierra for a few days. Sometimes, the light will turn off on its own after the PCM confirms the leak is fixed. If it doesn’t, proceed to the next step.
Use an OBD2 Scanner to Read the Code
Locate the OBD2 port under the dashboard, usually on the driver’s side near the steering column. Plug in your scanner and turn the ignition to the “ON” position (but don’t start the engine). Follow the scanner’s instructions to read the trouble code.
The scanner will display a code like P0455 (large evaporative leak) or P0171 (system too lean). Write it down or take a photo. Then, use the scanner’s built-in database or search online to understand what the code means.
For example, a P0300 code indicates random/multiple cylinder misfires, which could point to bad spark plugs, ignition coils, or fuel injectors. A P0420 code suggests a failing catalytic converter.
Inspect Related Components
Based on the code, inspect the suspected parts. For a P0135 code (O2 sensor heater circuit), check the sensor’s wiring and connector. For a P0171, look for vacuum leaks, dirty MAF sensors, or clogged fuel injectors.
If you’re not comfortable diagnosing or repairing the issue, take your truck to a trusted mechanic. Fixing the problem is essential—resetting the light won’t make the issue disappear.
Step 2: Fix the Underlying Issue
Once you’ve identified the problem, it’s time to fix it. Here are common repairs for the 2017 GMC Sierra.
Replace the Gas Cap
If the code points to an evaporative emissions leak (P0440–P0457), replacing the gas cap is often the solution. OEM (original equipment manufacturer) caps are recommended for a proper seal. After installation, tighten it until you hear it click three times.
Clean or Replace the MAF Sensor
A dirty mass airflow sensor can cause lean codes (P0171, P0174). Remove the sensor (usually held by two screws), spray it with MAF cleaner (do not use brake cleaner or compressed air), and let it dry completely before reinstalling.
Replace Spark Plugs and Ignition Coils
Misfire codes (P0300–P0308) often stem from worn spark plugs or faulty coils. The 2017 Sierra uses coil-on-plug ignition, so each cylinder has its own coil. Replace plugs every 60,000–100,000 miles and coils as needed. Use a torque wrench to avoid over-tightening.
Address O2 Sensor Issues
O2 sensors monitor exhaust gases and help the PCM adjust the air-fuel mixture. A failing sensor can reduce fuel economy and increase emissions. Replacement involves unplugging the electrical connector and using an O2 sensor socket to remove the old unit. Install the new one and reconnect the wiring.
Check for Vacuum Leaks
Vacuum leaks can cause lean conditions and rough idling. Inspect hoses for cracks, splits, or loose connections. Use a smoke machine or spray carb cleaner around hoses while the engine is running—if the RPMs change, you’ve found a leak.
After completing the repair, double-check all connections and ensure everything is properly secured.
Step 3: Reset the Check Engine Light
Now that the issue is fixed, it’s time to reset the check engine light. There are three main methods: using an OBD2 scanner, disconnecting the battery, or driving until the light turns off. We’ll cover each in detail.
Method 1: Use an OBD2 Scanner (Recommended)
This is the safest and most effective way to reset the light.
- Turn off the engine and locate the OBD2 port.
- Plug in the scanner and turn the ignition to “ON.”
- Follow the scanner’s menu to access the “Clear Codes” or “Erase DTCs” option.
- Confirm the action when prompted.
- The scanner will display a message like “Codes cleared” or “Reset successful.”
- Turn off the ignition and unplug the scanner.
The check engine light should be off when you restart the truck. If it comes back on immediately, the problem may not be fully resolved, or a new issue has been detected.
Method 2: Disconnect the Battery
This method resets the PCM by cutting power, but it comes with risks.
- Turn off the engine and remove the key.
- Open the hood and locate the battery.
- Use a wrench to loosen the negative (black) terminal clamp.
- Disconnect the negative cable and wait 15–30 minutes. This allows the PCM’s capacitors to discharge.
- Reconnect the cable and tighten the clamp securely.
- Start the truck. The light should be off.
Warning: Disconnecting the battery can reset radio presets, climate settings, and adaptive transmission learning. On some models, it may also trigger the “Service Theft System” message. Use this method only if you don’t have an OBD2 scanner.
Method 3: Drive Until the Light Turns Off
In some cases, the light will turn off on its own after the PCM confirms the issue is fixed. This requires completing a “drive cycle”—a series of driving conditions that allow the onboard diagnostics to run tests.
For the 2017 GMC Sierra, a typical drive cycle includes:
- Cold start (engine off for at least 8 hours)
- Idle for 2–3 minutes
- Drive at 30–40 mph for 5 minutes
- Accelerate to 55–60 mph and cruise for 10 minutes
- Decelerate without braking (coast in gear)
- Repeat for 3–5 cycles
If the problem is resolved, the light should turn off after a few drive cycles. However, this method is unreliable for persistent issues and may take days or weeks.
Step 4: Verify the Reset
After resetting the light, it’s important to confirm the fix was successful.
Monitor the Dashboard
Start the truck and check that the check engine light remains off. If it flashes or comes back on, the issue persists.
Use the OBD2 Scanner Again
Plug in the scanner and check for pending or stored codes. If no codes appear, the system is clean. If codes return, further diagnosis is needed.
Complete a Drive Cycle
Even after clearing the code, your truck needs to complete a full drive cycle to ensure all monitors are ready. This is especially important if you plan to get an emissions test.
Most 2017 Sierras require several monitors to be “ready,” including:
- Catalyst monitor
- O2 sensor monitor
- Evaporative system monitor
- EGR monitor (if equipped)
You can check monitor status with an OBD2 scanner. If any are “not ready,” continue driving until they complete.
Troubleshooting Common Issues
Sometimes, resetting the check engine light doesn’t go as planned. Here’s how to handle common problems.
Light Comes Back On Immediately
If the light returns right after resetting, the problem wasn’t fully fixed. Recheck your repairs. For example, a new gas cap may still have a defective seal, or an O2 sensor may be intermittently failing.
Scanner Won’t Clear Codes
Some scanners can’t clear certain codes if the issue is still active. Ensure the problem is resolved before attempting to reset. Also, make sure the ignition is on and the scanner is compatible with your vehicle.
Battery Disconnect Causes Other Issues
If you disconnected the battery and now have radio or transmission issues, you may need to reset adaptive systems. For the radio, re-enter your security code (found in the owner’s manual or glove box). For the transmission, drive normally for 100–200 miles to allow the PCM to relearn shift patterns.
Check Engine Light Flashes While Driving
A flashing light indicates a severe misfire that can damage the catalytic converter. Pull over safely, turn off the engine, and call for a tow. Do not continue driving.
Preventing Future Check Engine Light Issues
The best way to avoid check engine light problems is through regular maintenance.
Follow the Maintenance Schedule
Refer to your owner’s manual for the recommended service intervals. Key items for the 2017 Sierra include:
- Oil and filter change every 7,500 miles (or 12 months)
- Air filter replacement every 15,000–30,000 miles
- Spark plug replacement every 60,000–100,000 miles
- Fuel system cleaning every 30,000 miles
- Transmission fluid change every 100,000 miles
Use Quality Fuel and Parts
Fill up at reputable gas stations to avoid contaminated fuel. Use OEM or high-quality aftermarket parts for repairs. Cheap sensors or caps may fail prematurely.
Inspect Hoses and Belts
Check vacuum hoses, serpentine belts, and coolant hoses during oil changes. Replace cracked or brittle components before they cause problems.
Keep the Engine Clean
A clean engine runs more efficiently and is easier to diagnose. Use an engine degreaser to remove oil and grime, but avoid spraying electrical components.
When to See a Mechanic
While many check engine light issues can be resolved at home, some require professional help.
Seek a mechanic if:
- The light is flashing
- You’re unsure of the diagnosis
- The code points to a complex issue (e.g., transmission, PCM, or internal engine problem)
- The light returns after multiple resets
- You lack the tools or confidence to perform repairs
A certified technician has advanced diagnostic tools and experience with GMC vehicles. They can perform a thorough inspection and ensure the repair is done correctly.
Conclusion
Resetting the check engine light on your 2017 GMC Sierra doesn’t have to be intimidating. By diagnosing the problem first, using the right tools, and following proper procedures, you can clear the light safely and effectively. Whether you use an OBD2 scanner, disconnect the battery, or complete a drive cycle, the key is to fix the underlying issue—not just hide the warning.
Remember, the check engine light is your truck’s way of asking for help. Ignoring it can lead to costly repairs down the road. But with the knowledge from this guide, you’re equipped to respond wisely. Stay proactive with maintenance, address issues early, and your Sierra will continue to deliver reliable performance for years to come.