Changing tire size can throw off your speedometer and odometer readings. If you’ve recently upgraded to larger or smaller tires, you might be wondering how to correct this inaccuracy. Can you use an OBD2 scanner to change your speedometer? The answer is yes, with the right tools and a little know-how. This guide will walk you through the process of adjusting your speedometer for new tires using an OBD2 scanner and the JScan app.
Correcting Speedometer Inaccuracies with OBD2 and JScan
Upgrading to all-terrain or plus-sized tires is a popular modification, but it often leads to inaccurate speedometer readings. This discrepancy occurs because the vehicle’s computer calculates speed based on the original tire size. When the tire diameter changes, the actual speed differs from what the speedometer displays. This not only affects speed readings but also the odometer, potentially leading to incorrect mileage tracking.
Fortunately, you can rectify this issue using an OBD2 scanner and the JScan app. Here’s a step-by-step guide:
Tools You’ll Need
- OBD2 Scanner: A Bluetooth OBD2 scanner that connects to your smartphone is necessary. Recommended options include the Veepeak OBDCheck Bluetooth OBD II Scanner and the Vgate iCar Pro Bluetooth 4.0 (BLE) OBD2 Scanner. These are readily available online.
- Smartphone with JScan App: Download the JScan app on your Android or iPhone. Note that a paid license for the app is required to access the necessary features for adjusting tire size.
- Tape Measure: You’ll need to accurately measure your new tire diameter.
Measuring Your Tires
While online tire size calculators can provide an estimated diameter, it’s crucial to measure your actual tire. Measure from the top of the tire to the bottom, ensuring the tape measure is perpendicular to the ground. This measurement will be used in the JScan app.
Using JScan to Adjust Speedometer Readings
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Connect the OBD2 Scanner: Plug the OBD2 scanner into your vehicle’s OBD2 port, usually located under the dashboard on the driver’s side.
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Connect to JScan: Pair your smartphone with the OBD2 scanner via Bluetooth and launch the JScan app. Follow the app’s instructions to establish a connection to your vehicle.
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Navigate to Tire Size Settings: Within the JScan app, find the settings related to tire size or vehicle configuration. The exact location may vary depending on the vehicle model.
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Input the New Tire Diameter: Enter the measured tire diameter (in inches) into the appropriate field in JScan.
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Confirm and Save: Double-check the entered value and confirm the change. Allow the system a few minutes to process the adjustment.
Verifying the Adjustment
After making the change, verify the accuracy of your speedometer using a GPS device or a reliable speed-tracking app on your smartphone. Drive at various speeds and compare the readings to ensure the adjustment was successful.
Important Considerations
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Connection Issues: You might encounter connection issues with the OBD2 scanner. Try restarting the app, disconnecting and reconnecting the scanner, or starting the engine.
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Processing Time: Allow sufficient time for JScan to process the tire size change. It may take a couple of minutes.
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Unexpected Errors: Although rare, unexpected errors or warning lights might occur after adjusting settings. If this happens, consult a qualified mechanic.
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Disclaimer: Modifying vehicle settings can potentially void warranties or cause unforeseen issues. Proceed with caution and only adjust settings you understand. This guide is for informational purposes only and should not be considered professional advice. Consult a qualified mechanic if you have any doubts or concerns.
This process empowers you to accurately calibrate your speedometer after changing tire sizes, ensuring accurate speed and mileage readings. Remember to always prioritize safety and consult a professional if you encounter any difficulties.
