Experiment with your TomTom to establish how far out of calibration it is. See how far to the left or right your finger must be for the correct function to be selected. Do the same again, for the up-and-down orientation. Make detailed notes; they’ll come in handy later.
Shut off your TomTom and remove the SD card, if it has one. Press the power button to restart the GPS. Once you hear the TomTom drumbeat, press and hold the power button. Eventually, a dark screen with white text will appear.
Look for a line reading “Touchscreen Calibration Data.” It will list four numbers separated by spaces. Those numbers will vary between models, but might read something like “110 920 115 865.” These represent the minimum and maximum values for your left-right and up-down positions. Write them down.
Create a new text file on your computer using Notepad. Name it “cal.txt,” without quotes, if you’re using a current TomTom with version 8.051 or later of the company’s GPS software. If your GPS uses an older version of the software, name it “calib.txt,” again without the quotes.
Type the original calibration data from your TomTom — just those four numbers — into the Notepad document. If you’re using a current TomTom, change the order to put the higher number first in each pair. The order should then be high-low-high-low. If you’re using the older software, change only the first pair. Your order should be high-low-low-high. Save the file.
Connect your TomTom to the computer and turn it on. Close TomTom HOME if it opens. Use Windows Explorer to copy the “cal.txt” or “calib.txt” file to your TomTom or its SD card.
Disconnect the TomTom and test it again. It should behave exactly as it did before, which is the desired result. Now you’re ready to start calibrating the screen.
Re-connect your TomTom to the computer using a USB cable, and shut down TomTom HOME if it opens. Open Windows Explorer, and click on the icon representing your TomTom or its memory card. Open the “cal.txt” or “calib.txt” file.
Change the numbers in the text file slightly. For example, if your touch screen is skewed to the right, reduce the first pair of numbers by 10 or 15 to bring the alignment left. Save the file, disconnect your TomTom from the computer, and restart it. Your touch screen should be closer to its original alignment.
Connect the TomTom to the computer once more, and repeat your changes to the calibration numbers. Reduce or increase the first pair in small increments to move your calibration left or right, and the second pair to move it up and down. Save the file, and test your TomTom again.
Repeat this trial-and-error process until you’ve restored your unit to correct calibration. Copy this revised calibration data file to your computer for later reference, so you can compare the original and new calibration numbers.