Modern vehicles are significantly more complex than their counterparts from the 1990s, boasting about ten times the number of control units. This increased sophistication means that a vast range of issues can now be identified simply by analyzing error codes. This is where On-Board Diagnostics (OBD2) scanners become invaluable.
Learning how to use an OBD2 scanner can save you considerable time and money on car maintenance and repairs. This guide provides everything a typical car owner needs to understand about these devices.
What is an OBD2 Scanner and What Does it Do?
An OBD2 scanner is a powerful diagnostic tool that connects to a dedicated port in your car to gather data from its various control units. This data includes diagnostic trouble codes (DTCs), commonly known as fault codes, as well as real-time information, or live data, such as pressure, temperature, and speed readings.
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This wealth of information originates from numerous sensors throughout your vehicle. Typically, fault codes are triggered when a sensor reading falls outside of the acceptable range or when a sensor stops responding altogether.
More advanced diagnostic scanners offer enhanced capabilities, including performing service functions and even coding. Coding is often necessary when replacing specific components in today’s vehicles, ensuring the new part communicates correctly with the car’s computer system.
On-board diagnostic systems became a standard feature in all cars manufactured from 1996 in the United States and from 2004 in Europe, making OBD2 scanners universally applicable to most modern vehicles.
Types of OBD2 Scanners: Finding the Right Tool for You
The market offers a wide variety of OBD2 scanners to suit different needs and budgets. The most basic and affordable option is a Bluetooth OBD2 code reader, which pairs with your smartphone via a mobile app. These devices are generally inexpensive and capable of reading fault codes and displaying basic live data, making them a practical choice for everyday drivers seeking a simple way to understand their car’s health.
For those who are more inclined towards DIY car repairs, investing in a more feature-rich OBD2 scanner is advisable. These scanners often provide the ability to reset service lights, activate service procedures for tasks like replacing brake pads, and access a broader range of live data parameters. Prices for these mid-range scanners typically start around $100 and increase depending on the level of functionality they offer.
However, standard OBD2 scanners may not always meet the demands of professional mechanics. Automotive technicians require tools that can handle everything from routine maintenance, such as oil changes, to complex engine repairs. For professionals, the extensive coding and programming capabilities found in professional-grade OBD2 diagnostic tools are essential.
With the right professional tools, an experienced automotive electrician can fine-tune virtually every customizable setting in a modern car. However, these advanced systems come with a significant price tag, often costing thousands of dollars, and are generally too complex for the average user.
Step-by-Step Guide: How to Read OBD2 Fault Codes
Reading fault codes is the foundational step in OBD2 diagnostics. If you want to effectively use an OBD2 scanner, understanding this process is crucial. While the controls can vary across different scanner models, the fundamental procedure remains largely consistent.
1. Connecting Your OBD2 Scanner
All modern cars are equipped with an OBD2 port, typically located beneath the steering wheel or within the center console area. This port is often concealed by a small plastic cover. Locate the port and securely plug in your OBD2 scanner.
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Many contemporary scanners and code readers utilize Bluetooth for wireless connectivity. If you’re using a Bluetooth scanner, ensure it is properly paired with your device.
2. Turning On the Ignition
Computer diagnostics via an OBD2 scanner require the car’s ignition to be switched on. Before initiating a scan, turn the ignition to the “ON” position. To minimize battery drain during the process, it’s recommended to turn off unnecessary electrical loads like headlights, radio, and air conditioning.
While most vehicles permit fault code scanning with the engine running, fault codes are stored in the car’s computer memory and will persist until manually cleared. However, starting the engine can be beneficial when analyzing live data, as it allows you to observe sensor readings under operating conditions.
3. Selecting Your Vehicle
Once the OBD2 scanner is connected and the ignition is on, you will typically need to input your vehicle’s details, including make, model, and year. This information is essential for the scanner to correctly identify the car’s control units and interpret the data accurately.
Many modern diagnostic tools feature an automatic vehicle recognition system that automatically detects the car’s VIN number and configures the necessary settings. Alternatively, you can manually enter the VIN if the automatic recognition fails.
4. Initiating a Fault Code Scan
Finally, select the option to read fault codes from the scanner’s menu. Most scanners offer a choice between scanning specific control units or performing a comprehensive scan of all available modules.
If you encounter difficulties navigating the scanner’s interface, consult the integrated help section or the user manual for detailed instructions on locating these options.
The duration of a full system scan can range from a few seconds to several minutes, depending on the vehicle model and the complexity of its electronic systems.
5. Interpreting Fault Codes
The fault codes retrieved during the scan are the underlying cause of warning lights illuminating on your dashboard. In some instances, fault codes are relatively self-explanatory. For example, a code like “C0035 – Right Front Wheel Speed Sensor Circuit Malfunction” clearly indicates a problem with the right front ABS wheel speed sensor. This likely suggests the sensor needs replacement.
However, the root causes of fault codes can often be more intricate than they initially appear. For instance, “P0171 – System Too Lean (Bank 1)” signifies that the air-fuel mixture is too lean, but this issue could stem from a variety of factors, such as a clogged fuel filter, a failing fuel pump, a vacuum leak, various sensor malfunctions, or other potential problems.
Pro Tip: Utilizing Live Data for Deeper Diagnostics
The ability to access and interpret live data significantly enhances your diagnostic capabilities. Most control units within your car provide a dedicated section for live data, allowing you to monitor sensor readings in real-time. How can this be helpful?
Consider a scenario where your car is experiencing a noticeable loss of power, and the only fault code present is related to limp mode activation. In such cases, examining live data can be invaluable. You can monitor parameters like fuel pressure, boost pressure (if applicable), intake airflow, and intake manifold pressure to determine if they are within normal operating ranges. Deviations from expected values can provide crucial clues in pinpointing the source of the problem.
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However, even with access to fault codes and live data, accurately diagnosing complex automotive issues can be challenging. You may still need to consult repair manuals, online resources, or seek professional assistance to fully understand the fault codes and effectively troubleshoot the underlying problems.
OBD2 Scanners: A Key Tool When Buying a Used Car
The used car market, unfortunately, can present risks for buyers. Unscrupulous sellers may attempt to offload vehicles with hidden issues, ranging from undisclosed accident history to electrical faults or even legal encumbrances.
While vehicle history reports are invaluable for uncovering a car’s past, a thorough pre-purchase inspection is essential to protect yourself from unexpected and costly repairs.
Before finalizing the purchase of a used vehicle, it is always recommended to obtain a vehicle history report and, crucially, to check for fault codes using an OBD2 scanner. If you don’t own an OBD2 scanner or are unsure about how to use one effectively, it’s wise to have the car inspected by a qualified mechanic before you buy.
Clearing Fault Codes: What Happens After Repairs?
Scanning for fault codes is a crucial step in diagnosing car problems, but fault codes themselves often don’t directly pinpoint the exact cause. Even when a diagnostic scan indicates a faulty mass airflow sensor, experienced technicians will typically test the sensor using a multimeter to confirm the diagnosis before replacing it. This is because fault codes can sometimes be misleading, arising from issues like damaged wiring, loose connections, or corrosion rather than a faulty sensor itself.
Once the underlying problem has been identified and rectified, it’s essential to clear the fault codes and rescan the system. If the fault code does not reappear, it’s a strong indication that the issue has been successfully resolved, and you can confidently get back on the road.
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Article by
Evaldas Zabitis
Evaldas has been writing since middle school and has had a lifelong passion for cars. He has extensive hands-on experience fixing, driving, and selling cars. Evaldas stays up-to-date with automotive technical innovations and actively participates in automotive community discussions.
