How To Reset Check Engine Light Subaru: A Comprehensive Guide

Resetting the check engine light on your Subaru is possible through several methods, including using an OBD-II scanner or performing a battery disconnect. CAR-TOOL.EDU.VN offers detailed information and tools to help you diagnose and resolve the underlying issue efficiently, preventing future occurrences and ensuring your Subaru runs smoothly. Understanding the causes and solutions will save you time and money.

1. Understanding the Check Engine Light on Your Subaru

The check engine light (CEL), also known as the malfunction indicator lamp (MIL), is a component of your Subaru’s onboard diagnostics (OBD) system. When the light illuminates, it signals that one or more of the vehicle’s sensors have detected a problem. This problem could range from minor issues like a loose gas cap to severe issues like engine misfires or catalytic converter failure. Understanding the potential reasons for the CEL is the first step in effectively addressing the issue. According to the Environmental Protection Agency (EPA), OBD systems are designed to monitor the performance of major engine components, including those responsible for controlling emissions.

1.1 Common Reasons for the Check Engine Light to Illuminate

Several common issues can trigger the check engine light in your Subaru. Identifying these causes can help you narrow down the problem and take appropriate action:

• Loose or Faulty Gas Cap: A loose gas cap is one of the most frequent causes. The gas cap prevents fuel vapors from escaping the fuel system, and when it’s loose or damaged, it can trigger an EVAP (evaporative emission control system) code.
• Oxygen Sensor Issues: Oxygen sensors measure the amount of oxygen in the exhaust gases. A faulty oxygen sensor can affect the engine’s air-fuel mixture, leading to reduced fuel efficiency and potential engine damage.
• Catalytic Converter Failure: The catalytic converter reduces harmful emissions from the exhaust. If it fails, the check engine light will illuminate, and the vehicle may fail an emissions test.
• Mass Airflow (MAF) Sensor Problems: The MAF sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor can cause the engine to run poorly, resulting in a CEL.
• Spark Plug or Ignition Coil Issues: Worn or damaged spark plugs and faulty ignition coils can cause engine misfires, which trigger the check engine light.
• Vacuum Leaks: Vacuum leaks can disrupt the engine’s air-fuel mixture, leading to rough idling and a CEL.
• EVAP System Problems: Issues within the evaporative emission control system can trigger the CEL. This system captures fuel vapors to prevent them from being released into the atmosphere.
• Faulty Sensors: Various other sensors, such as the crankshaft position sensor or the camshaft position sensor, can cause the CEL to illuminate if they fail.

1.2 Interpreting the Check Engine Light: Solid vs. Flashing

The behavior of the check engine light itself can provide clues about the severity of the issue:

• Solid Check Engine Light: A solid, constantly lit check engine light typically indicates a problem that needs attention but is not immediately critical. It’s advisable to have the vehicle inspected soon, but you can generally continue driving.
• Flashing Check Engine Light: A flashing check engine light signifies a severe problem, such as an engine misfire, that could quickly damage the engine or catalytic converter. It’s crucial to stop driving as soon as safely possible and have the vehicle towed to a repair shop.

Understanding the difference between a solid and flashing CEL can help you make informed decisions about how to proceed and prevent further damage to your Subaru.

2. Preliminary Steps Before Resetting the Check Engine Light

Before you reset the check engine light on your Subaru, it’s essential to take a few preliminary steps to ensure you’re not just masking a problem that could worsen over time. Ignoring the underlying issue can lead to more extensive and costly repairs down the road.

2.1 Inspecting the Gas Cap

The first and simplest step is to check the gas cap. Ensure it is tightly closed. A loose gas cap can cause a leak in the evaporative emission control system, triggering the check engine light. Remove the gas cap, inspect it for cracks or damage, and then re-tighten it until you hear a click.

2.2 Checking for Obvious Issues

Perform a visual inspection of the engine compartment. Look for any obvious signs of damage, such as disconnected hoses, frayed wires, or fluid leaks. Check the engine oil level and coolant level to ensure they are within the recommended ranges. Addressing these simple issues can sometimes resolve the problem and prevent the check engine light from coming back on.

2.3 Record any Abnormal Symptoms

Before resetting the check engine light, make a note of any unusual symptoms your Subaru has been exhibiting. These can include:

• Rough idling
• Reduced fuel economy
• Hesitation during acceleration
• Unusual noises from the engine
• Changes in exhaust smell

Recording these symptoms will provide valuable information for a mechanic if the check engine light reappears, helping them diagnose the problem more efficiently.

2.4 Using an OBD-II Scanner to Read the Code

The most effective way to determine why the check engine light is on is to use an OBD-II (on-board diagnostics II) scanner. This tool plugs into the OBD-II port, usually located under the dashboard, and reads the diagnostic trouble codes (DTCs) stored in the vehicle’s computer.

1. Connect the Scanner: Plug the OBD-II scanner into the OBD-II port.
2. Turn On the Ignition: Turn the ignition key to the “on” position without starting the engine.
3. Read the Codes: Follow the scanner’s instructions to read the diagnostic trouble codes.
4. Record the Codes: Write down all the codes displayed by the scanner. These codes will provide specific information about the problem.

2.5 Researching the Diagnostic Trouble Codes (DTCs)

Once you have the DTCs, research them to understand what they mean. Websites like CAR-TOOL.EDU.VN offer comprehensive databases of OBD-II codes and their possible causes. For example, a code like “P0420” indicates a problem with the catalytic converter efficiency, while “P0171” suggests a lean fuel mixture.

Understanding the meaning of the codes will help you decide whether you can fix the problem yourself or if you need to take the vehicle to a professional mechanic.

3. Methods to Reset the Check Engine Light on a Subaru

After diagnosing the issue causing the check engine light to illuminate, you can proceed with resetting it. There are several methods to accomplish this, each with its own advantages and disadvantages.

3.1 Using an OBD-II Scanner to Reset the Light

The most reliable way to reset the check engine light is using an OBD-II scanner. Most scanners have a built-in function to clear diagnostic trouble codes and reset the CEL.

1. Connect the Scanner: Plug the OBD-II scanner into the OBD-II port.
2. Turn On the Ignition: Turn the ignition key to the “on” position without starting the engine.
3. Clear the Codes: Follow the scanner’s instructions to clear the diagnostic trouble codes. This function is often labeled as “Clear Codes,” “Erase Codes,” or something similar.
4. Verify the Reset: After clearing the codes, start the engine and check if the check engine light is off. If it remains on, there may be a persistent issue that needs further attention.

Using an OBD-II scanner ensures that the check engine light is reset properly and allows you to monitor if the codes reappear, indicating a recurring problem.

3.2 Disconnecting the Battery to Reset the Light

Another method to reset the check engine light is by disconnecting the vehicle’s battery. This process removes power from the vehicle’s computer, causing it to reset and clear any stored diagnostic trouble codes. However, this method should be used with caution, as it can also reset other electronic systems, such as the radio presets and security system.

1. Gather Your Tools: You will need a wrench (usually 10mm) and gloves to protect your hands.
2. Locate the Battery: The battery is typically located in the engine compartment, but in some Subaru models, it may be under the rear seat or in the trunk.
3. Disconnect the Negative Terminal: Using the wrench, loosen the nut on the negative (-) battery terminal. Carefully remove the cable from the terminal.
4. Wait: Wait for 15-20 minutes. This allows the vehicle’s computer to fully discharge and reset.
5. Reconnect the Negative Terminal: Reattach the negative (-) battery cable to the terminal and tighten the nut securely.
6. Start the Engine: Start the engine and check if the check engine light is off.

Precautions:

• Make sure the engine is turned off before disconnecting the battery.
• Avoid touching the positive (+) terminal with the wrench while disconnecting the negative (-) terminal to prevent a short circuit.
• Be aware that disconnecting the battery will reset the radio presets and other electronic settings.

3.3 Driving Cycle Method

In some cases, the check engine light may turn off automatically after the vehicle completes a “driving cycle.” A driving cycle is a set of specific driving conditions that allow the vehicle’s computer to run all the necessary diagnostic tests.

A typical driving cycle involves:

1. Cold Start: Start the engine after it has been sitting for several hours.
2. Idling: Allow the engine to idle for a few minutes.
3. Moderate Acceleration: Drive the vehicle at a moderate speed with gentle acceleration.
4. Cruising: Maintain a steady speed on the highway for several minutes.
5. Deceleration: Allow the vehicle to decelerate without using the brakes.
6. Stop and Idle: Come to a complete stop and let the engine idle for a few more minutes.

The exact driving cycle requirements can vary depending on the Subaru model and the specific diagnostic trouble code. Consult your vehicle’s repair manual or a trusted mechanic for the correct procedure.

3.4 Using a Code Reader App on Your Smartphone

Modern technology has made it possible to use smartphone apps to read and reset diagnostic trouble codes. These apps work in conjunction with a Bluetooth or Wi-Fi OBD-II scanner that plugs into the vehicle’s OBD-II port.

1. Purchase an OBD-II Scanner: Buy a compatible Bluetooth or Wi-Fi OBD-II scanner. These scanners are widely available online and at auto parts stores.
2. Download an App: Download a compatible code reader app on your smartphone. Popular options include Torque Pro, OBD Fusion, and Car Scanner ELM OBD2.
3. Connect the Scanner: Plug the OBD-II scanner into the OBD-II port.
4. Pair with Your Smartphone: Follow the app’s instructions to pair the scanner with your smartphone via Bluetooth or Wi-Fi.
5. Read and Clear Codes: Use the app to read the diagnostic trouble codes and clear them.

Smartphone apps offer a convenient way to monitor your vehicle’s health and reset the check engine light on the go.

4. When to Seek Professional Help

While resetting the check engine light can be a simple task, there are situations where it’s best to seek professional help from a qualified mechanic.

4.1 Recurring Check Engine Light

If the check engine light comes back on shortly after you reset it, it indicates that the underlying problem has not been resolved. Continuing to drive with a recurring CEL can lead to further damage and more costly repairs.

4.2 Serious Symptoms

If your Subaru exhibits serious symptoms such as:

• Severe engine misfires
• Loss of power
• Excessive smoke from the exhaust
• Unusual noises from the engine

It’s crucial to have the vehicle inspected by a professional mechanic immediately.

4.3 Complex Diagnostic Trouble Codes

Some diagnostic trouble codes can be complex and require specialized knowledge and equipment to diagnose properly. If you encounter codes that you’re unfamiliar with or that require in-depth troubleshooting, it’s best to consult a mechanic.

4.4 Lack of Experience

If you’re not comfortable working on your vehicle or lack the necessary tools and experience, it’s always a good idea to seek professional help. A qualified mechanic can accurately diagnose and repair the problem, ensuring your Subaru is running safely and efficiently.

5. Preventing the Check Engine Light from Returning

Once you’ve addressed the issue causing the check engine light to illuminate, it’s essential to take steps to prevent it from returning. Regular maintenance and proactive care can help keep your Subaru running smoothly and avoid future problems.

5.1 Regular Maintenance

Follow the manufacturer’s recommended maintenance schedule for your Subaru. This includes:

• Changing the engine oil and filter regularly
• Replacing the air filter and fuel filter as needed
• Inspecting and replacing spark plugs
• Checking and topping off fluid levels
• Inspecting belts and hoses for wear and damage

Regular maintenance helps ensure that all components are functioning correctly and can prevent many common issues that trigger the check engine light.

5.2 Proper Fuel and Gas Cap Hygiene

Always use the correct type of fuel recommended for your Subaru. Using lower-octane fuel than recommended can cause engine knocking and trigger the check engine light. Also, make sure to tighten the gas cap properly after each refueling to prevent evaporative emission control system leaks.

5.3 Monitoring Vehicle Performance

Pay attention to how your Subaru is running and be alert for any changes in performance. If you notice any unusual symptoms, such as rough idling, reduced fuel economy, or hesitation during acceleration, have the vehicle inspected by a mechanic as soon as possible.

5.4 Addressing Issues Promptly

Don’t ignore minor problems or put off repairs. Addressing issues promptly can prevent them from escalating into more significant and costly problems that trigger the check engine light.

5.5 Using Quality Parts

When replacing parts on your Subaru, always use high-quality, OEM (original equipment manufacturer) or reputable aftermarket parts. Cheap, low-quality parts may fail prematurely and cause the check engine light to come on. CAR-TOOL.EDU.VN can assist you in finding reliable and durable parts for your vehicle.

6. Advanced Diagnostic Tools and Techniques

For more complex issues that trigger the check engine light, advanced diagnostic tools and techniques may be necessary to pinpoint the root cause.

6.1 Live Data Streaming

OBD-II scanners with live data streaming capabilities can provide real-time information about various engine parameters, such as:

• Oxygen sensor readings
• Fuel trim values
• Engine temperature
• MAF sensor readings
• Ignition timing

Analyzing this data can help identify problems that may not be apparent from diagnostic trouble codes alone.

6.2 Smoke Testing

Smoke testing is a technique used to detect vacuum leaks in the engine. A smoke machine is connected to the intake system, and smoke is forced through the system. Any leaks will be revealed by the escaping smoke.

6.3 Multimeter Testing

A multimeter can be used to test the voltage, resistance, and continuity of various electrical components, such as sensors, switches, and wiring. This can help identify faulty components or wiring problems that may be causing the check engine light to illuminate.

6.4 Oscilloscope Diagnostics

An oscilloscope is an advanced diagnostic tool that can display electrical signals in a graphical format. This can be useful for diagnosing complex electrical problems, such as intermittent sensor failures or wiring issues.

7. Common Diagnostic Trouble Codes for Subaru Vehicles

Here’s a list of common diagnostic trouble codes (DTCs) that are frequently encountered in Subaru vehicles, along with their typical causes and potential solutions.

DTC Code	Description	Common Causes	Potential Solutions
P0011	“A” Camshaft Position Timing Over-Advanced or System Performance (Bank 1)	Low oil level, faulty oil control valve, timing belt misalignment, camshaft position sensor issue	Check oil level, replace oil control valve, inspect timing belt, replace camshaft position sensor
P0014	“B” Camshaft Position Timing Over-Advanced or System Performance (Bank 1)	Low oil level, faulty oil control valve, timing belt misalignment, camshaft position sensor issue	Check oil level, replace oil control valve, inspect timing belt, replace camshaft position sensor
P0026	Intake Valve Control Solenoid Circuit Range/Performance (Bank 1)	Faulty intake valve control solenoid, wiring issues	Replace intake valve control solenoid, check wiring and connections
P0028	Exhaust Valve Control Solenoid Circuit Range/Performance (Bank 1)	Faulty exhaust valve control solenoid, wiring issues	Replace exhaust valve control solenoid, check wiring and connections
P0102	Mass or Volume Air Flow Circuit Low Input	Dirty or faulty MAF sensor, vacuum leaks, wiring issues	Clean or replace MAF sensor, check for vacuum leaks, check wiring and connections
P0113	Intake Air Temperature Circuit High Input	Faulty IAT sensor, wiring issues	Replace IAT sensor, check wiring and connections
P0128	Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)	Faulty thermostat, coolant level too low, faulty coolant temperature sensor	Replace thermostat, check coolant level, replace coolant temperature sensor
P0131	O2 Sensor Circuit Low Voltage (Bank 1, Sensor 1)	Faulty oxygen sensor, exhaust leaks, wiring issues	Replace oxygen sensor, check for exhaust leaks, check wiring and connections
P0171	System Too Lean (Bank 1)	Vacuum leaks, dirty MAF sensor, faulty oxygen sensor, fuel pump issues, clogged fuel filter	Check for vacuum leaks, clean MAF sensor, replace oxygen sensor, check fuel pump, replace fuel filter
P0301	Cylinder 1 Misfire Detected	Faulty spark plug, faulty ignition coil, faulty fuel injector, low compression, vacuum leaks	Replace spark plug, replace ignition coil, replace fuel injector, check compression, check for vacuum leaks
P0302	Cylinder 2 Misfire Detected	Faulty spark plug, faulty ignition coil, faulty fuel injector, low compression, vacuum leaks	Replace spark plug, replace ignition coil, replace fuel injector, check compression, check for vacuum leaks
P0303	Cylinder 3 Misfire Detected	Faulty spark plug, faulty ignition coil, faulty fuel injector, low compression, vacuum leaks	Replace spark plug, replace ignition coil, replace fuel injector, check compression, check for vacuum leaks
P0304	Cylinder 4 Misfire Detected	Faulty spark plug, faulty ignition coil, faulty fuel injector, low compression, vacuum leaks	Replace spark plug, replace ignition coil, replace fuel injector, check compression, check for vacuum leaks
P0420	Catalyst System Efficiency Below Threshold (Bank 1)	Faulty catalytic converter, faulty oxygen sensors, exhaust leaks	Replace catalytic converter, replace oxygen sensors, check for exhaust leaks
P0442	Evaporative Emission Control System Leak Detected (Small Leak)	Loose or faulty gas cap, faulty EVAP system components (purge valve, vent valve, hoses)	Tighten or replace gas cap, inspect and replace EVAP system components
P0447	Evaporative Emission Control System Vent Control Circuit Open	Faulty vent control valve, wiring issues	Replace vent control valve, check wiring and connections
P0455	Evaporative Emission Control System Leak Detected (Gross Leak)	Loose or faulty gas cap, faulty EVAP system components (purge valve, vent valve, hoses)	Tighten or replace gas cap, inspect and replace EVAP system components
P0500	Vehicle Speed Sensor “A”	Vehicle Speed Sensor faulty, wiring issues	Replace Vehicle Speed Sensor, check wiring and connections
P0700	Transmission Control System (MIL Request)	Internal transmission problems, faulty sensors, wiring issues	Consult a transmission specialist
P0730	Incorrect Gear Ratio	Internal transmission problems, low transmission fluid level, faulty sensors	Consult a transmission specialist, check transmission fluid level
P1443	Evaporative Emission Control System Purge Control Valve Circuit	Faulty purge control valve, wiring issues	Replace purge control valve, check wiring and connections
P1518	Starter Switch Circuit Low Input	Faulty starter switch, wiring issues	Replace starter switch, check wiring and connections

8. Understanding Subaru Specific Systems

Subaru vehicles often include unique systems that, when malfunctioning, can trigger the check engine light. Familiarizing yourself with these can aid in more accurate diagnoses.

8.1 Subaru’s Symmetrical All-Wheel Drive (AWD)

Subaru’s Symmetrical All-Wheel Drive (AWD) system ensures power is delivered to all wheels, enhancing traction and handling. However, issues within the AWD system itself can sometimes trigger the check engine light. This is often related to wheel speed sensor malfunctions, transmission issues, or problems with the Vehicle Dynamics Control (VDC) system.

8.2 Subaru’s EyeSight Driver Assist System

The EyeSight system incorporates cameras and sensors to provide features like adaptive cruise control, lane departure warning, and pre-collision braking. Malfunctions within the EyeSight system can sometimes cause the check engine light to illuminate, often accompanied by other warning lights on the dashboard.

8.3 Subaru’s Active Valve Control System (AVCS)

Subaru’s Active Valve Control System (AVCS) optimizes engine performance by adjusting valve timing based on driving conditions. Problems with the AVCS, such as faulty oil control valves or camshaft position sensors, can trigger the check engine light.

8.4 Subaru’s Electronic Throttle Control (ETC)

The Electronic Throttle Control (ETC) system manages the throttle valve electronically, optimizing engine performance and fuel efficiency. Issues within the ETC system, such as a faulty throttle position sensor or a dirty throttle body, can cause the check engine light to illuminate.

9. Frequently Asked Questions (FAQ)

1. How long can I drive with the check engine light on in my Subaru?

It depends on whether the light is solid or flashing. A solid light indicates a problem that should be addressed soon, but you can generally continue driving. A flashing light indicates a severe problem, such as an engine misfire, and you should stop driving as soon as safely possible.

2. Will the check engine light turn off by itself on my Subaru?

Yes, in some cases, the check engine light may turn off automatically after the vehicle completes a driving cycle and the problem is no longer present. However, it’s best to address the underlying issue to prevent it from returning.

3. Can a loose gas cap cause the check engine light to come on in my Subaru?

Yes, a loose gas cap is a common cause of the check engine light. Make sure the gas cap is tightened properly after each refueling.

4. How do I find the OBD-II port in my Subaru?

The OBD-II port is typically located under the dashboard on the driver’s side. It’s usually near the steering column or in the vicinity of the pedals.

5. What is an OBD-II scanner, and how does it work?

An OBD-II scanner is a tool that plugs into the OBD-II port and reads diagnostic trouble codes (DTCs) stored in the vehicle’s computer. These codes provide specific information about the problem causing the check engine light to illuminate.

6. Can I use a smartphone app to reset the check engine light on my Subaru?

Yes, you can use a smartphone app in conjunction with a Bluetooth or Wi-Fi OBD-II scanner to read and reset diagnostic trouble codes.

7. What does it mean if the check engine light is flashing in my Subaru?

A flashing check engine light indicates a severe problem, such as an engine misfire, that could quickly damage the engine or catalytic converter. Stop driving as soon as safely possible and have the vehicle towed to a repair shop.

8. Is it safe to disconnect the battery to reset the check engine light on my Subaru?

Disconnecting the battery can reset the check engine light, but it should be used with caution as it can also reset other electronic systems, such as the radio presets and security system.

9. What should I do if the check engine light comes back on shortly after I reset it?

If the check engine light comes back on shortly after you reset it, it indicates that the underlying problem has not been resolved. Seek professional help from a qualified mechanic.

10. Where can I find reliable information about Subaru diagnostic trouble codes?

Websites like CAR-TOOL.EDU.VN offer comprehensive databases of OBD-II codes and their possible causes, helping you understand and address the issues effectively.

10. Conclusion

Resetting the check engine light on your Subaru can be a straightforward task, especially when you understand the underlying causes and have the right tools. Whether you choose to use an OBD-II scanner, disconnect the battery, or perform a driving cycle, it’s essential to address the root cause of the problem to prevent it from recurring. CAR-TOOL.EDU.VN is your trusted partner for finding reliable parts and tools, and provides the information you need to keep your Subaru running smoothly.

For expert advice and assistance in selecting the right tools and parts for your Subaru, contact us today. Our team at CAR-TOOL.EDU.VN is here to help you diagnose and resolve any issues you may be experiencing.

Contact Information:

• Address: 456 Elm Street, Dallas, TX 75201, United States
• Whatsapp: +1 (641) 206-8880
• Website: CAR-TOOL.EDU.VN

Don’t wait for minor issues to turn into major problems. Contact CAR-TOOL.EDU.VN today and let us help you keep your Subaru in top condition.

By following these steps and staying informed, you can effectively manage your Subaru’s check engine light and ensure its long-term reliability.