Modern vehicles are significantly more complex than cars from the 1990s, boasting ten times the number of control units. This increased complexity means a greater capacity for self-diagnosis, which is where OBD2 scanners become invaluable. By understanding how to use an OBD2 scanner, you can save considerable time and money on car repairs and maintenance. This guide provides everything you need to know about using these powerful diagnostic tools.
What is an OBD2 Scanner and What Does it Do?
An OBD2 scanner is a diagnostic tool that connects to your car’s onboard computer system through a designated port. Once connected, it retrieves data from the vehicle’s control units, offering insights into your car’s health. This data includes crucial fault codes and live data parameters such as pressure readings, temperature levels, and speed.
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The information gathered by an OBD2 scanner originates from various sensors throughout your vehicle. Typically, fault codes are triggered when a sensor reading falls outside of acceptable limits or when a sensor ceases to respond altogether.
More advanced OBD2 diagnostic tools extend beyond basic fault code reading. They can perform service functions like resetting maintenance reminders, activating procedures for tasks such as brake pad replacement, and even handle coding for replacing specific components in newer car models.
On-board diagnostics (OBD2) systems became a standard feature in all cars manufactured for the US market from 1996 onwards, and for European vehicles from 2004. This standardization ensures broad compatibility across a wide range of vehicles.
Types of OBD2 Scanners
The market offers a diverse range of OBD2 scanners to suit different needs and budgets. For basic diagnostics, a Bluetooth OBD2 code reader represents the most affordable entry point. These compact devices pair with your smartphone, allowing you to read fault codes and access basic live data through a mobile app. These readers are inexpensive and user-friendly, making them a practical choice for the average car owner.
For individuals who prefer DIY car maintenance and repairs, investing in a more capable OBD2 scanner is recommended. These mid-range scanners not only read fault codes and live data but also offer functionalities like resetting service lights, initiating service procedures for tasks like brake service, and providing more extensive live data streams. Prices for these scanners typically start around $100 and increase based on their features and capabilities.
Professional mechanics and automotive technicians require the most advanced OBD2 diagnostic tools. While standard OBD2 scanners are useful, they lack the comprehensive features needed for complex repairs and diagnostics. Professional-grade OBD2 diagnostic tools provide extensive coding and programming capabilities, enabling technicians to manage everything from routine oil changes to complete engine replacements.
These advanced systems allow for intricate adjustments and configurations within a modern vehicle’s electronic systems. However, professional OBD2 tools come with a significant price tag, often costing thousands of dollars, and are designed for users with specialized training and expertise.
Step-by-Step Guide: How to Use an OBD2 Scanner
Reading fault codes is the fundamental function of OBD2 diagnostics. Mastering this process is the first and most crucial step in learning how to use an OBD2 scanner effectively. While the controls and interface may vary across different models, the basic procedure remains consistent.
1. Connect the Scanner
Every modern car is equipped with an OBD2 port. This port is typically located beneath the steering wheel or within the center console area. You might need to look under a plastic cover to find it. Once located, firmly plug your OBD2 scanner into this port.
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Many contemporary scanners and code readers utilize Bluetooth for wireless connectivity. If you are using a Bluetooth scanner, ensure it is properly paired with your smartphone or device according to the manufacturer’s instructions.
2. Turn on the Ignition
OBD2 scanners require the car’s electrical system to be active to perform diagnostics. Therefore, you must turn on the ignition before initiating a scan. To minimize electrical load during the process, it’s advisable to turn off unnecessary accessories like headlights, radio, and air conditioning.
In most vehicles, you can perform a fault code scan with the engine either running or off, but with the ignition turned on. Fault codes are stored in the car’s computer memory and will persist until manually cleared. However, running the engine is often beneficial when you intend to examine live data readings, as these readings reflect real-time sensor values during operation.
3. Choose Your Vehicle
After connecting the OBD2 scanner and turning on the ignition, the next step is to input your vehicle’s information into the scanner. This typically involves selecting the car’s make, model, and year. This information is essential for the diagnostic tool to correctly identify the vehicle’s control units and interpret the data accurately.
Many modern OBD2 scanners are equipped with an automatic VIN (Vehicle Identification Number) recognition system. This feature automatically detects your car’s VIN and configures the necessary vehicle specifications for you. If automatic VIN recognition is not available or unsuccessful, you can manually enter the VIN. Knowing what is a VIN number and where to find it on your vehicle is helpful for this step.
4. Scan for Fault Codes
Once the vehicle information is entered, navigate the scanner’s menu to find the fault code reading option. Most scanners offer the choice to scan specific control units or perform a comprehensive scan of all available units. For a general diagnostic check, a full system scan is usually recommended.
If you encounter difficulty locating these options, consult the user manual or the scanner’s built-in help section. These resources will provide specific guidance on navigating the scanner’s interface and initiating a fault code scan.
The duration of a full system scan varies depending on the vehicle’s model and the number of control units. It can range from a few seconds to several minutes.
5. Inspect Revealed Fault Codes
The fault codes displayed after the scan are the key to understanding why warning lights may be illuminated on your dashboard. Some fault codes are straightforward and clearly indicate the problem. For example, a code like “C0031- Rear Right Wheel Speed Sensor Circuit” strongly suggests a problem with the rear right ABS sensor, possibly requiring replacement.
However, it’s important to understand that fault codes often point to a symptom rather than the root cause of the problem. For instance, a common code “P0171 – System Too Lean (Bank 1)” indicates that the engine’s fuel mixture is too lean. This condition can be triggered by a variety of issues, including a clogged fuel filter, a failing fuel pump, a vacuum leak, sensor malfunctions, or other underlying problems.
Pro tip: Reading Live Data
Beyond fault codes, the ability to read live data is a powerful feature of OBD2 scanners that can greatly aid in diagnosing complex car issues. Most diagnostic tools provide a live data section, allowing you to monitor real-time sensor readings from various systems. How can this be beneficial?
Consider a scenario where your car is experiencing a noticeable loss of power, and the only fault code reported is related to “limp mode” activation. In such cases, examining live data can provide crucial clues. You can monitor parameters such as fuel pressure, boost pressure (for turbocharged engines), intake airflow, and intake manifold pressure to check if these values are within their normal operating ranges. Deviations from expected values can help pinpoint the source of the problem.
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While OBD2 scanners offer valuable diagnostic capabilities, interpreting fault codes and live data effectively often requires automotive knowledge and experience. For complex issues, consulting a professional mechanic is advisable.
OBD2 Scanners and Used Car Inspections
The used car market can present challenges for buyers. Sellers may not always disclose a vehicle’s full history or existing problems. Electrical issues, hidden damage, or even legal discrepancies can be masked.
While obtaining a vehicle history report is a crucial step in used car due diligence, a thorough pre-purchase inspection is essential to mitigate the risk of unexpected repair costs.
Before finalizing the purchase of a used car, always run a history report and use an OBD2 scanner to check for fault codes. If you are unfamiliar with how to use an OBD2 scanner or lack confidence in interpreting the results, it is wise to have the vehicle inspected by a qualified mechanic before purchase.
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How to Get Rid of Fault Codes
Scanning for fault codes is a diagnostic step, and the codes themselves often don’t directly reveal the exact fix. Even when a diagnostic scan indicates a faulty mass airflow sensor, experienced technicians will typically use a multimeter to test the sensor and confirm the diagnosis before replacing parts. Surprisingly often, fault codes can arise from issues like damaged wiring, loose connections, or corrosion rather than a faulty sensor itself.
Once the underlying problem has been identified and repaired, it’s essential to re-scan for fault codes. If the code no longer reappears after the repair, the issue is likely resolved. You can then typically clear the stored fault codes using your OBD2 scanner. Consult your scanner’s manual for instructions on how to clear codes. After clearing the codes and confirming that no new codes emerge, you can confidently get back on the road.
Frequently Asked Questions
Article by
Evaldas Zabitis
Evaldas has been writing since middle school and has had a passion for cars for as long as he can remember. Right after getting his driver’s license, he spent all of his savings on shoddy cars so he could spend time fixing, driving, and selling them. Evaldas is always interested in automotive technical innovations and is an active participant in automotive community discussions.
