How to Fix a Phone Fingerprint Scanner That Stopped Working

Published 2026-10-14 · Marion Phone Repair

A fingerprint scanner that worked yesterday but will not recognize your finger today is frustrating, especially when you are locked out of your phone or forced to type your PIN every time. The good news is that most fingerprint scanner failures are temporary and caused by something on the surface of your finger or the sensor, not a hardware problem.

Clean the sensor and your finger

Fingerprint sensors read the ridges of your fingertip through capacitive sensing (detecting tiny electrical differences) or optical imaging (taking a picture of the print through the screen). Anything between your finger and the sensor reduces accuracy.

• Clean the sensor. For phones with a dedicated fingerprint button (back or side of the phone), wipe it with a dry microfiber cloth. For in-display scanners (under-screen), clean the area of the screen where the fingerprint icon appears. Even a thin layer of oil or moisture can block the scan
• Clean your finger. Dry your finger thoroughly. Wash off any lotion, sunscreen, cooking oil, or grime. Wet or oily fingers are the single most common cause of fingerprint failures
• Check for cuts or dry skin. A cut, blister, peeling skin, or extremely dry cracked skin on the registered fingertip changes the print pattern enough to cause rejections. If your fingertip is damaged, use a different finger or your PIN until it heals

Check your screen protector

Screen protectors are one of the most common causes of fingerprint scanner problems, especially on phones with in-display (under-screen) sensors like newer Samsung Galaxy, Google Pixel, and OnePlus phones.

• Thick tempered glass protectors often block or weaken the fingerprint sensor signal. Ultrasonic and optical in-display scanners need to read through the protector, and thick glass reduces the signal significantly
• Air bubbles over the sensor area scatter the signal and cause inconsistent reads. If there is a bubble right where the fingerprint icon appears, the scanner will fail frequently
• Protectors not designed for your phone model may not have the correct cutout or may be the wrong thickness for the sensor type

To test: remove the screen protector entirely and try the fingerprint scanner. If it works perfectly without the protector, replace it with a thinner one specifically designed for your phone model, or re-register your fingerprints with the new protector in place (see below).

Samsung phones have a Touch Sensitivity option (Settings, Display, Touch Sensitivity) that increases sensor sensitivity to compensate for screen protectors. Turn this on if you use one.

Delete and re-register your fingerprints

Over time, the stored fingerprint data can become less accurate, especially if you registered your print with a different screen protector, with wet hands, or if the sensor's calibration has drifted after a software update. Re-registering gives the sensor a fresh, clean read.

iPhone (Touch ID)

1. Go to Settings, Touch ID and Passcode
2. Enter your passcode
3. Tap each saved fingerprint and tap Delete Fingerprint
4. Tap Add a Fingerprint. Place your finger on the home button and lift it repeatedly, adjusting your angle each time. Cover the entire surface of your fingertip, including the edges
5. Register the same finger twice for better accuracy. You have five fingerprint slots

Samsung Galaxy (in-display or side button)

1. Go to Settings, Biometrics and Security, Fingerprints
2. Enter your PIN or pattern
3. Remove all saved fingerprints
4. Tap Add Fingerprint. Press firmly on the sensor and lift, adjusting your angle with each press. Samsung recommends roughly 15 to 20 presses to complete registration
5. Register with the screen protector already installed if you use one. A print registered without a protector will not work well through one

Google Pixel

1. Go to Settings, Security, Fingerprint Unlock
2. Enter your PIN
3. Delete existing prints and add new ones
4. For the Pixel's under-display sensor, press firmly and cover the full area of the fingerprint icon on screen

Software troubleshooting

Restart the phone

A simple restart fixes a surprising number of fingerprint scanner issues. The sensor driver or the biometric service can hang after extended use, background process conflicts, or incomplete software updates. Restarting clears these states.

Check for software updates

Fingerprint scanner bugs appear occasionally in OS updates and are typically patched quickly. Check for updates in Settings, General, Software Update (iPhone) or Settings, System, Software Update (Android). Samsung's monthly security updates frequently include biometric improvements.

Safe Mode (Android)

If the fingerprint scanner stopped working after installing a new app, the app may be interfering with the biometric system. Boot into Safe Mode (hold the power button, then press and hold Power Off until Safe Mode appears) and test the fingerprint scanner. If it works in Safe Mode, a recently installed app is the problem. Uninstall recent apps one at a time to identify which one.

Hardware causes

If cleaning, re-registration, and software troubleshooting do not fix the scanner, the hardware may be damaged:

• Water damage. Moisture inside the phone can corrode the sensor contacts or the flex cable connecting the sensor to the motherboard. If the phone was recently exposed to water and the scanner stopped working, water damage is the likely cause even if the phone otherwise works fine
• Drop damage. A drop can crack the sensor (especially side-mounted and rear-mounted sensors), disconnect the flex cable, or damage the under-display sensor layer. The sensor may appear physically intact but no longer function
• Worn sensor surface. On phones with physical fingerprint buttons, years of daily use can wear down the sensor surface, reducing its ability to read prints accurately. This is gradual and most noticeable on phones older than 3 to 4 years
• Screen replacement with non-original parts. If the phone's screen was previously replaced, the replacement screen may not include the same quality in-display sensor, or the sensor may not be properly calibrated to the new display

Fingerprint scanner repair in Marion

Marion Phone Repair diagnoses and fixes fingerprint scanner problems on iPhones, Samsung Galaxy, Google Pixel, and other phones. We test the sensor hardware, replace damaged modules, and handle screen-related sensor issues. Most repairs are completed same-day.