Upgrading your vehicle’s tires can significantly enhance its appearance and performance, especially if you’re switching to all-terrain tires for off-road adventures. However, changing tire sizes, even slightly, can throw off the accuracy of your speedometer and odometer. If you’ve recently installed new tires and noticed your speedometer reading seems inaccurate, you’re not alone. This article will guide you through how to easily recalibrate your speedometer using an OBD2 scanner and a smartphone app, focusing on the “Speedometer Obd2” method for a precise fix.
It’s a common scenario: you’ve swapped out your old tires for a set that better suits your needs, like going from a 235/55/r17 to a 225/65/r17, as one Jeep Patriot owner experienced. While seemingly minor, this change in tire dimension directly impacts the rolling circumference of your wheels. The vehicle’s computer uses the rotations of your wheels to calculate speed and distance. When you install tires with a different overall diameter than the original factory specification, the computer miscalculates these values, leading to an inaccurate speedometer reading. For instance, with larger diameter tires, your speedometer might indicate 60 mph when you’re actually traveling at 64 mph, as highlighted by our featured Jeep Patriot owner. This discrepancy not only affects your speedometer but also slightly undercounts your vehicle’s mileage on the odometer over time.
Fortunately, there’s a straightforward solution to correct this issue and ensure your speedometer and odometer are accurate again. The key lies in utilizing your vehicle’s OBD2 (On-Board Diagnostics II) port, a standard feature in modern cars, and an affordable OBD2 scanner along with a user-friendly smartphone application.
Tools You’ll Need for Speedometer Recalibration via OBD2
To recalibrate your speedometer after a tire size change, you will need the following tools:
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OBD2 Scanner: This device plugs into your car’s OBD2 port and communicates with your vehicle’s computer system. There are numerous OBD2 scanners available on the market. Bluetooth-enabled scanners are particularly convenient as they wirelessly connect to your smartphone. Popular options include the Veepeak Bluetooth OBD2 Scanner and the Vgate Bluetooth OBD2 Scanner, both readily available online.
Alt Text: Veepeak Bluetooth OBD2 Scanner, a tool for speedometer OBD2 calibration, pictured against a white background.
Alt Text: Vgate Bluetooth OBD2 Scanner, another option for speedometer OBD2 adjustment, displayed on a white surface. -
Smartphone with JScan App: The JScan application is a powerful tool designed for Jeep, Chrysler, Dodge, and Ram vehicles. It allows you to access and modify various vehicle settings, including tire size for speedometer calibration. JScan is available for both Android and iOS devices. It’s important to note that JScan requires a license purchase, which costs approximately $20, to unlock its full functionality, including the ability to change tire sizes.
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Tape Measure: While online tire size converters can provide theoretical tire diameters, actual tire dimensions can vary slightly. For the most accurate speedometer calibration, you’ll need a tape measure to physically measure the diameter of your newly installed tires.
Step-by-Step Guide to Recalibrating Your Speedometer Using OBD2 and JScan
Once you have gathered the necessary tools, follow these steps to recalibrate your speedometer using the OBD2 method and the JScan app:
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Connect the OBD2 Scanner: Locate the OBD2 port in your vehicle. In most vehicles, including the Jeep Patriot, it’s typically found under the dashboard on the driver’s side. Plug your OBD2 scanner securely into the port.
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Install and Set Up JScan App: Download and install the JScan app on your smartphone. Launch the app and follow the initial setup prompts, selecting your vehicle’s make and model. You will likely be prompted to purchase a license at this stage to enable tire size adjustments and other advanced features. Activate your license within the app.
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Connect JScan to OBD2 Scanner: Enable Bluetooth on your smartphone and pair it with your OBD2 scanner through the JScan app. You may need to follow the scanner’s instructions for pairing. Ensure a stable Bluetooth connection between your phone and the OBD2 scanner. You might need to try connecting a few times if you encounter initial connection issues. Sometimes turning the vehicle’s ignition to the “ON” position (engine not started) or starting the engine can help establish a connection.
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Measure Your Tire Diameter: For optimal accuracy, physically measure the diameter of your tires. Using a tape measure, measure from the very top to the very bottom of your tire while it is installed on your vehicle and properly inflated. Record this measurement in inches. While online tire size converters might suggest a diameter, actual measurements can differ slightly, as observed by the Jeep Patriot owner who measured their 225/65/r17 tires to be just over 27 inches, rather than the approximately 28.5 inches predicted by online converters.
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Enter Tire Size in JScan: Within the JScan app, navigate to the section that allows for vehicle configuration or adaptations. Look for settings related to “tire size,” “wheel size,” or “speedometer calibration.” The JScan app may display your current tire size setting, often in inches. Input the measured tire diameter you obtained in the previous step into the app. JScan might present the tire size setting in inches, as it did for the Jeep Patriot owner who found their stock tire size diameter listed as 26.5 inches.
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Apply and Save Changes: After entering the new tire diameter, confirm and apply the changes within the JScan app. The app will communicate with your vehicle’s computer to update the tire size parameter. Be patient during this process; it may take a minute or two for the changes to be processed and saved to your vehicle’s system. Do not exit the app or disconnect the OBD2 scanner during this time.
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Verify Speedometer Accuracy: Once the changes are applied, test your speedometer to ensure it’s now accurate. Use a GPS-based speedometer app on your smartphone (like Google Maps or “Car Scanner ELM OBD2,” as suggested in the original guide) or compare your speedometer reading against roadside speed signs while driving at a constant speed. Make minor adjustments in JScan if necessary to fine-tune the calibration.
Important Considerations and Troubleshooting
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Connection Issues: As noted by the original Jeep Patriot owner, you might experience initial difficulties establishing a Bluetooth connection between your phone and the OBD2 scanner. Try closing and reopening the JScan app, disconnecting and reconnecting the OBD2 scanner, and ensuring your vehicle’s ignition is in the “ON” position or the engine is running.
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Wait for Changes to Process: When submitting tire size changes in JScan, allow sufficient time for the app to process the request and update your vehicle’s computer. Be patient and avoid interrupting the process.
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Caution with Settings: The JScan app offers access to numerous vehicle settings. Exercise caution and only change settings you are certain about. Incorrectly modifying other parameters could lead to unexpected issues or malfunctions. The original author experienced a temporary ABS light illumination after making changes, which thankfully resolved itself. However, this highlights the importance of being careful and only adjusting the intended settings.
Conclusion
Recalibrating your speedometer after a tire size upgrade using an OBD2 scanner and the JScan app is a relatively simple and cost-effective DIY procedure. By following these steps, you can ensure your speedometer and odometer accurately reflect your vehicle’s speed and mileage, maintaining safety and accuracy. Using the “speedometer obd2” method with JScan empowers you to take control of your vehicle’s settings and enjoy the benefits of your new tires without compromising speedometer precision. This method saves you time and money compared to dealership recalibration services, making it an excellent option for car enthusiasts and DIYers alike.
