Master Your Subaru: Easy Guide to Reading & Clearing Fault Codes
Subaru, the Japanese automaker known for its all-wheel-drive vehicles and adventurous spirit, utilizes Diagnostic Trouble Codes (DTCs) to identify and diagnose potential issues within its vehicles. Standardized by the Society of Automotive Engineers (SAE), these codes provide valuable insights into the health of various vehicle systems, enabling technicians to troubleshoot and repair faults effectively. Fortunately, Diagnostic Trouble Codes (DTCs) are valuable for identifying and addressing these problems before they become major inconveniences. Over 20 warning lights could illuminate your dashboard, including ABS, SRS, transmission temperature, oil pressure, battery charging, differential, and tract control. That is why it is important to know about these lights and error codes to retain the performance and safety of your vehicle.
When the check engine light comes on, it is important to have your vehicle scanned for fault codes. We have an in-depth article if you need to learn more specifically about Subaru check engine light.
DTCs are like Morse codes from your Subaru, revealing hidden issues that might hinder their optimal performance. These alphanumeric codes provide clues to underlying problems, empowering mechanics or DIY enthusiasts to diagnose and repair them efficiently. Understanding DTCs will help many people, especially vehicle owners, stay informed about their vehicle’s health and make informed decisions about its maintenance.
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Accessing Subaru fault codes and erasing codes
To unravel the mysteries of these automotive enigmas, you’ll need an OBD-II scanner, and you’ll even need a professional-grade scanner to read all systems such as airbags, transmissions, SRS, ABS, climate control, etc. This handy device acts as a decoder, translating the cryptic codes into a language we can comprehend. In this section, we’ll delve into details of reading and erasing DTC/Fault codes of your Subaru with models like WRX, WRX STI, Legacy, Impreza, and many newer or older models. Once connected to your Subaru’s diagnostic port, the scanner will display the fault codes, typically five-digit codes.
- Gather the necessary tools: Equip yourself with a Professional-Grade OBD-II Scanner compatible with your Subaru. See our Professional-Grade YOUCANIC Scanner.
- Access the OBD-II Port: This port is usually found under the dashboard, near the steering column; the OBD-II port is the gateway to your car’s diagnostic information. Turn the ignition key to the “ON” position without starting the engine to make a connection with the vehicle’s computer. If your Subaru has a START/STOP feature, press the button without pressing the brake pedal. Do not start the engine. If you are unsure of the OBD-II port of your vehicle, you can always check the Car Owner’s Manual. If you can’t find the OBD-II port’s location, check out – Subaru OBD-II port Location.
- Access the Diagnostic Menu: On the YOUCANIC scanner’s display, navigate to the “Diagnostic” or “Scan” menu. This menu allows you to access various diagnostic functions for your Subaru.
- Select ‘SUBARU’ as the Vehicle Make: This ensures the scanner effectively communicates with the Subaru’s onboard diagnostic system and effectively scans the fault codes.
- Select option for model selection: The scanner has various options; you can choose SmartVIN to detect your vehicle automatically. However, you choose Manual Selection if SmartVIN does not work as intended. Learn more about your Subaru’s VIN number here.
- Select the Specific Model and Chassis: After selecting the vehicle make, scroll through the available models and select the correct one for your Subaru. Choose the corresponding chassis or body type to sync the scanner to your vehicle properly.
- Select Control Units: Once you have selected the model and chassis, the scanner will let you choose between “Quick scan” or “Control Modules.” Control Modules display a list of control units or modules in your vehicle. Examples include the engine control module (ECM), transmission control module (TCM), and ABS control module. Choose the specific module you want to diagnose. Otherwise, you can also choose the “Quick Scan” to check everything.
- Interpret the Codes: Once the YOUCANIC scanner completes the code retrieval process, the displayed codes will provide information about specific issues detected by the control unit. Take note of these codes for further analysis and diagnosis. Each DTC consists of a letter and four numbers. The letter indicates the system affected, while the numbers describe the issue more specifically. Click here to learn more about fault codes.
- Erase Codes: After the problem has been repaired, return to the scanner’s menu and select the option to “Erase Codes” or “Clear Codes.” This action removes the stored fault codes from the control unit’s memory, indicating that the problem has been resolved. Please note that you may or may not erase a code when the issue is not fixed.
NOTE: These pictures are just the demo of our YOUCANIC Scanner. It may or may not be the same, but the procedure is the same.
Is it okay to scan Subaru fault codes always?
Regularly scanning your Subaru for DTCs is akin to giving your vehicle a check-up. It’s recommended to scan your car at least once a year or more frequently if you notice any performance issues or warning lights illuminating. Check our article here if you want to know more about the warning lights on your Subaru.
Why do I need to scan my vehicle?
There are several reasons why you should scan your vehicle for fault codes:
- To identify the source of the problem. Fault codes can help you pinpoint the specific problem with your vehicle. This can save you time and money on repairs.
- To prevent further damage. Ignoring fault codes can lead to further damage to your vehicle and be dangerous.
- It can improve fuel efficiency, and fixing problems causing fault codes can improve a vehicle’s fuel efficiency depending on the malfunctioning part.
- To pass emission testing in some states, you may be required to have your vehicle scanned for fault code before you can pass emission testing.
One of our articles about the best OBD-II Scanner for DIY Enthusiasts is here: Best OBD2 Scanner For DIY Auto Repair – YOUCANIC.
Why can’t I clear my Subaru’s fault codes?
Once you’ve identified the DTCs, you may be tempted to clear them, hoping to continue driving your Subaru, and the problem magically disappears. Clearing the codes can temporarily remove the “Check Engine” light, but it doesn’t address the underlying issue. It will always come back. Here are also some lists of why you cannot clear the codes of your Subaru:
- Use a Professional-Grade Scanner: Ditch the generic scanner and upgrade to a professional-grade one like the YOUCANIC scanner. YOUCANIC, on the other hand, is like the master key to your Subaru’s diagnostics, unlocking hidden diagnostic powers and letting you clear codes that would otherwise remain stubborn and hidden.
- Underlying Issues: Before clearing fault codes, remember to address the underlying issue that triggered them in the first place. Clearing codes is like patching a leaky pipe without fixing the cracked valve – it’s just a temporary fix. The ‘check engine’ light will surely come back and haunt you.
- Continuous Fault Monitoring: Like the ABS or CEL light, specific fault codes may be cleared by disconnecting the battery (like a reset). They will reappear even after clearing until the root cause is resolved. It is a persistent reminder to fix the problem, not just mask it.
- Proper Clearing Procedure: Following the correct steps outlined in your diagnostic scanner’s user manual is essential to clear fault codes effectively. If unsure about the clearing procedure, consult a professional for guidance specific to your scanner and Subaru model.
What happens when I ignore the fault codes?
It can lead to several problems, like further damage to your vehicle, because the problem causing the fault code may get worse and cause further damage. Ignoring fault codes can lead to increased emissions, harming the environment. Failure to pass emission testing could happen if you ignore fault codes; you may not be able to pass the emission testing in your state.
Decoding the Enigma of Fault Codes
DTCs are standardized codes that follow a specific format, providing valuable insights into the nature of the problem. The first character indicates the type of system (P for powertrain, B for body, C for chassis, and U for network comm.), followed by four digits. The first digit identifies the system, the second digit denotes the subsystem, and the last two digits pinpoint the specific fault. 
For instance, a DTC starting with P01 would indicate a powertrain issue related to fuel or air metering. Further, a code like P0171 would point to a lean air-fuel mixture.
What do Historical, Current, and Stored DTCs do?
- History: These codes indicate past issues that have resolved themselves or are no longer causing the “Check Engine” light to illuminate. They typically do not require immediate attention.
- Current Codes: These codes represent current or active problems that require immediate diagnosis. They indicate a present issue or malfunction in a specific system or component of the vehicle that needs to be addressed. They will remain displayed until the underlying issue is resolved.
- Stored Codes: These codes are inactive but remain stored in the computer’s memory, recording previous issues. These can provide additional information about past issues as a historical reference for previous faults. While they may not be active, they can offer insights into the vehicle’s history and aid in the diagnostic process.
Please click here to learn more about the history, current, and stored DTCs.
What is the purpose of Live Data and Freeze data?
Live data allows you to monitor real-time sensor readings, providing valuable insights into the car’s operation. On the other hand, Freeze frame data captures a snapshot of vehicle conditions when a fault code is triggered. Analyzing this data provides context and aids in pinpointing the root cause of the issue.
Frequently Asked Questions:
Can I clear DTCs myself?
Yes! While clearing DTCs can temporarily turn off the “Check Engine” light, it doesn’t address the underlying issue. It’s recommended that a qualified mechanic diagnose and repair the problem before you clear all the codes. You can also ask for professional assistance.
How Often should I check for DTCs?
Regularly checking for DTCs can help you identify potential issues early, preventing more serious problems. You can also use it whenever a check engine light illuminates to diagnose or check why your car is acting up.
What are the benefits of using a professional-grade scanner?
Professional-grade scanners provide more detailed information, manufacturer-specific codes, guided diagnostics, and component testing capabilities, making them a valuable tool for accurate diagnosis and repair.
What are the most common Subaru DTCs?
The specific DTCs vary depending on the vehicle’s model and year. However, some common ones include P0171 (system too lean), P0304 (cylinder four misfires detected), and P0422 (catalyst system efficiency below threshold).
References:
- What Is an OBD2 Scanner and How Does It Work?
What Is an OBD2 Scanner and How Does It Work? | The Drive - DTC Fault Codes
DTC Fault Codes – YOUCANIC - What Does the Check Engine Light Look Like, and What Does It Mean?
What Does the Check Engine Light Look Like, and Really Mean? – Consumer Reports - Current / Stored / Active / Past / History Fault Codes Explained
Current / Stored / Active / Past / History Fault Codes Explained – YOUCANIC - A Guide to Understanding DTC Codes
A Guide to Understanding DTC Codes (samsara.com)
