Wondering how to get check engine light to go out? This guide walks you through diagnosing the issue, fixing common causes, and resetting the light—without unnecessary trips to the mechanic. Save time and money by tackling it yourself with confidence.
Key Takeaways
- Don’t ignore the light: Even if your car seems fine, the check engine light signals a problem that could worsen over time.
- Use an OBD2 scanner: This tool reads error codes and helps pinpoint the exact issue, saving guesswork.
- Check simple fixes first: Loose gas caps, dirty air filters, and old spark plugs are common culprits.
- Clear codes after repairs: Once fixed, use the scanner or disconnect the battery to reset the light.
- Drive normally after reset: The light may stay off after a few drive cycles if the problem is truly resolved.
- Seek professional help when needed: Complex issues like catalytic converter failure require expert diagnosis.
- Prevent future warnings: Regular maintenance reduces the chances of the light coming back on.
How to Get Check Engine Light to Go Out: A Complete DIY Guide
Seeing the check engine light pop up on your dashboard can be stressful. It’s like your car is whispering, “Hey, something’s not right,” but you’re not sure what. The good news? You don’t always need to rush to a mechanic. In many cases, you can figure out what’s going on and get that light to go out—all by yourself.
This guide will show you exactly how to get check engine light to go out safely and effectively. We’ll walk you through diagnosing the problem, fixing common issues, and resetting the light. Whether you’re a seasoned DIYer or a total beginner, these steps are simple, practical, and designed to save you time and money.
By the end of this guide, you’ll know how to read error codes, fix basic problems, and prevent the light from coming back. Let’s get started.
Step 1: Don’t Panic—Understand What the Light Means
First things first: don’t panic. The check engine light—also called the malfunction indicator lamp (MIL)—doesn’t always mean your car is about to break down. It simply means the onboard computer has detected a problem with the engine, emissions system, or related components.
Visual guide about How to Get Check Engine Light to Go Out
Image source: slashgear.com
The light can be steady or flashing. A steady light usually indicates a minor issue, like a loose gas cap. A flashing light, however, signals a serious problem—like a misfire that could damage the catalytic converter. If the light is flashing, pull over safely and consider calling for help.
Even if the light is steady, don’t ignore it. Problems can worsen over time, leading to poor fuel economy, reduced performance, or even engine damage. The sooner you address it, the better.
Common Causes of the Check Engine Light
- Loose or damaged gas cap
- Faulty oxygen (O2) sensor
- Worn spark plugs or ignition coils
- Dirty mass airflow (MAF) sensor
- Catalytic converter issues
- Evaporative emissions (EVAP) system leaks
- Exhaust gas recirculation (EGR) valve problems
Many of these issues are fixable at home with basic tools. Let’s move on to diagnosing the problem.
Step 2: Use an OBD2 Scanner to Read the Error Code
The most important step in how to get check engine light to go out is figuring out what’s causing it. That’s where an OBD2 (On-Board Diagnostics II) scanner comes in.
Every car made since 1996 has an OBD2 port, usually located under the dashboard near the steering wheel. This port connects to your car’s computer and allows you to read diagnostic trouble codes (DTCs). These codes tell you exactly what system or component is malfunctioning.
How to Use an OBD2 Scanner
- Locate the OBD2 port: It’s typically under the dashboard on the driver’s side. Look for a 16-pin connector.
- Plug in the scanner: Turn the ignition to the “ON” position (but don’t start the engine). Plug the scanner into the port.
- Turn on the scanner: Follow the device’s instructions to power it up.
- Read the codes: Press the “Scan” or “Read” button. The scanner will display one or more trouble codes (e.g., P0420, P0171).
- Write down the codes: Note them down or take a photo for reference.
Don’t have a scanner? Many auto parts stores (like AutoZone, O’Reilly, or Advance Auto Parts) offer free code reading. Just drive in, and they’ll hook up a scanner for you.
Understanding the Codes
OBD2 codes follow a standard format:
- P = Powertrain (engine, transmission)
- B = Body (airbags, climate control)
- C = Chassis (ABS, suspension)
- U = Network (communication between modules)
The next digit tells you if it’s a generic (0) or manufacturer-specific (1) code. The last four digits identify the specific issue.
For example, P0420 means “Catalyst System Efficiency Below Threshold (Bank 1).” This usually points to a failing catalytic converter.
Use a free online code lookup tool (like OBD-Codes.com) to decode your specific error. This will help you understand what needs fixing.
Step 3: Fix the Most Common Causes
Once you know the code, you can start troubleshooting. Let’s go over the most common fixes—starting with the simplest.
1. Tighten or Replace the Gas Cap
A loose, cracked, or missing gas cap is one of the top reasons the check engine light comes on. It allows fuel vapors to escape, triggering an EVAP system leak code (like P0455 or P0457).
How to fix it:
- Turn off the engine.
- Open the fuel door and remove the gas cap.
- Check for cracks, damage, or a worn seal.
- Tighten the cap until you hear it click 3–5 times.
- If the cap is damaged, replace it with an OEM or high-quality aftermarket cap.
After tightening or replacing the cap, drive for a few days. The light may turn off on its own after a few drive cycles.
2. Replace Spark Plugs and Ignition Coils
Worn spark plugs or faulty ignition coils can cause misfires, leading to codes like P0300 (random misfire) or P0301–P0308 (cylinder-specific misfires).
How to fix it:
- Locate the spark plugs (usually under the ignition coils on top of the engine).
- Remove one coil at a time and pull out the old spark plug.
- Check the plug for wear, carbon buildup, or damage.
- Replace with new plugs (use the manufacturer’s recommended type and gap).
- Reinstall the coil and repeat for each cylinder.
Tip: Replace all spark plugs at once, even if only one is bad. It ensures even performance and prevents future issues.
3. Clean or Replace the Mass Airflow (MAF) Sensor
A dirty MAF sensor can cause poor fuel economy, rough idling, and codes like P0171 (system too lean). The sensor measures how much air enters the engine, and dirt can throw off its readings.
How to fix it:
- Locate the MAF sensor (usually between the air filter box and the throttle body).
- Unplug the electrical connector.
- Remove the sensor using a screwdriver or socket.
- Spray it with MAF sensor cleaner (do not use water or compressed air).
- Let it dry completely, then reinstall.
If cleaning doesn’t help, consider replacing the sensor. It’s a relatively inexpensive part and can make a big difference.
4. Replace the Oxygen (O2) Sensor
The O2 sensor monitors exhaust gases and helps the engine adjust the air-fuel mixture. A faulty sensor can cause poor fuel economy and emissions issues (codes like P0130 or P0172).
How to fix it:
- Locate the O2 sensor (usually in the exhaust manifold or downpipe).
- Unplug the electrical connector.
- Use an O2 sensor socket to remove the old sensor.
- Install the new sensor and reconnect the wiring.
Note: Some vehicles have multiple O2 sensors (upstream and downstream). Make sure you’re replacing the right one.
5. Address EVAP System Leaks
The EVAP system prevents fuel vapors from escaping into the air. A leak—even a small one—can trigger the check engine light.
Common causes include cracked hoses, a faulty purge valve, or a damaged charcoal canister.
How to fix it:
- Inspect all EVAP hoses for cracks, splits, or loose connections.
- Check the purge valve (usually near the engine) for proper operation.
- Use a smoke machine (or visit a shop) to detect small leaks.
- Replace any damaged parts.
If you’re not comfortable with this, a mechanic can perform a smoke test to find the leak.
Step 4: Clear the Check Engine Light
Once you’ve fixed the problem, it’s time to turn off the light. There are two main ways to do this: using an OBD2 scanner or disconnecting the battery.
Method 1: Use an OBD2 Scanner
This is the easiest and most reliable method.
- Plug the scanner into the OBD2 port.
- Turn the ignition to “ON.”
- Navigate to the “Clear Codes” or “Erase DTCs” option.
- Confirm the action. The light should turn off immediately.
Tip: Some scanners also let you view live data or monitor readiness monitors—useful for emissions testing.
Method 2: Disconnect the Battery
If you don’t have a scanner, you can reset the computer by disconnecting the battery.
- Turn off the engine and remove the keys.
- Locate the negative (-) battery terminal.
- Use a wrench to loosen the clamp and disconnect the cable.
- Wait 15–30 minutes (this allows the computer to reset).
- Reconnect the cable and tighten it securely.
Note: This method may also reset your radio presets, clock, and other settings. Some vehicles require a relearn procedure for the idle speed.
Step 5: Drive and Monitor
After clearing the light, take your car for a drive. The computer needs to run through several “drive cycles” to confirm the problem is fixed.
A drive cycle typically includes:
- Starting the engine cold
- Driving at varying speeds
- Idling for a few minutes
- Turning off the engine
If the repair was successful, the light should stay off. If it comes back on, the problem may not be fully resolved—or there could be another issue.
Keep an eye on your car’s performance. Look for symptoms like rough idling, poor acceleration, or reduced fuel economy. These could indicate an ongoing problem.
Troubleshooting: What If the Light Comes Back On?
Sometimes, the check engine light turns off temporarily but returns after a few days. This means the root cause wasn’t fully addressed.
Common Reasons the Light Returns
- Incomplete repair: You fixed a symptom but not the underlying issue (e.g., replacing a sensor without fixing a vacuum leak).
- Intermittent problem: The issue only occurs under certain conditions (e.g., when the engine is cold or under load).
- Multiple problems: There’s more than one fault, and you only fixed one.
- Faulty repair: A new part was installed incorrectly or is defective.
What to Do Next
- Re-scan the vehicle to see if new codes appear.
- Check for technical service bulletins (TSBs) related to your car’s make and model.
- Consult a trusted mechanic if the problem persists.
Don’t keep clearing the light without fixing the issue. It’s like putting a bandage on a broken bone—it won’t help in the long run.
When to See a Mechanic
While many check engine light issues are DIY-friendly, some require professional help. Here’s when to call a mechanic:
- The light is flashing (indicates a severe misfire).
- You’re getting complex codes (like P0420 for catalytic converter failure).
- You’ve tried basic fixes and the light keeps coming back.
- You’re not comfortable working on your car.
- The car is running poorly, overheating, or making strange noises.
A professional mechanic has advanced tools and experience to diagnose and fix complex issues. It’s better to spend a little now than risk costly damage later.
How to Prevent the Check Engine Light from Coming Back
The best way to avoid future check engine light problems is through regular maintenance.
Maintenance Tips
- Change the oil regularly: Use the recommended oil type and change it every 3,000–7,500 miles.
- Replace air filters: A dirty air filter restricts airflow and can trigger codes.
- Use quality fuel: Cheap or contaminated gas can cause engine problems.
- Inspect belts and hoses: Look for cracks, wear, or leaks.
- Keep the gas cap tight: Always tighten it after filling up.
- Follow the maintenance schedule: Check your owner’s manual for service intervals.
Prevention is always cheaper than repair. A little care goes a long way.
Final Thoughts
Learning how to get check engine light to go out doesn’t have to be intimidating. With the right tools and a bit of patience, you can diagnose and fix many common issues yourself.
Start by reading the error code with an OBD2 scanner. Then, tackle simple fixes like tightening the gas cap or replacing spark plugs. Clear the light using the scanner or by disconnecting the battery. Finally, drive normally and monitor your car’s performance.
Remember: the check engine light is your car’s way of asking for help. Don’t ignore it. Addressing problems early saves money, improves safety, and keeps your car running smoothly.
With this guide, you’re now equipped to handle the check engine light like a pro. Stay proactive, stay informed, and enjoy the peace of mind that comes with a healthy, happy car.