How to Fix vivo Y51 Pro Biometrics Not Working

Dealing with a vivo Y51 Pro that refuses to recognize your fingerprint or face is one of those annoying things that can really ruin your morning.

I see this all the time in the shop where customers come in thinking their screen is broken or the sensor has died for good. Usually, it is just a simple setting conflict or a bit of stubborn dirt causing the whole mess.

Before we get into taking the phone apart, let us look at why these biometric sensors act up.

The Y51 Pro uses an optical in-display sensor which means it needs to actually see your fingerprint through the glass layers of the screen. If that glass is dirty or if the software is glitchy, the tiny camera under the display cannot get a clear picture of your ridges. Sometimes the face data gets corrupted after a system update or even just because the phone stayed on for too many days without a break.

I always listen closely to what the customer says about when the problem started. Did it happen after a drop, or did it just start getting slower and slower over time?

Clean the Fingerprint Sensor and Front Camera

Dust, oil, and moisture are the biggest enemies of any biometric scanner.

I have seen phones where the front camera was so covered in makeup or ear wax that the face unlock stood no chance at all. You should take a clean microfiber cloth and gently wipe the screen where the fingerprint icon appears.

Make sure your hands are not too dry or too wet because extreme skin conditions affect the reading.

1. Find a lint-free cloth or a very soft piece of cotton.
2. Wipe the area over the front camera lens and the lower part of the screen thoroughly.
3. Wash your hands to remove any grease that might be confusing the optical scanner.
4. Try to unlock the phone again to see if the responsiveness has improved.

Restart the Device to Clear Glitches

A simple restart is often the most underrated tool in my repair kit.

It clears the temporary cache and stops background processes that might be hogging the processor power needed for the security chip. I always tell my customers to try this first because it fixes about half of the software bugs I encounter.

If the biometric service has crashed in the background, a reboot will force it to start fresh.

Re-register Your Fingerprint and Face Data

The data stored in your phone can actually become outdated if you have scars or if your facial features change slightly.

Sometimes the initial scan was just poor quality because the lighting was bad or your finger was at a weird angle. I usually suggest deleting the old data and doing a fresh setup in a well-lit room.

1. Open the Settings app and navigate to the Fingerprint, face and password section.
2. Select Fingerprint and enter your backup PIN or pattern to gain access.
3. Delete all the existing fingerprints by tapping the trash icon next to each one.
4. Select Add fingerprint and follow the prompts to record your finger from every possible angle.
5. Do the same for the Face unlock by removing the old data and recording a new face scan in bright light.

This ensures the system has the most accurate map of your biometrics possible.

Check Your Screen Protector and Case

I have lost count of how many times a cheap tempered glass protector was the real criminal.

If the glass is too thick or if there is a tiny air bubble right over the sensor, the light cannot pass through properly. I often peel back the protector and find that the sensor works perfectly fine on the bare glass.

If you recently installed a new protector, that is likely why your vivo Y51 Pro is struggling now.

Adjust Power Saving Settings

Power saving modes are great for battery life but they can be aggressive with hardware performance.

When the phone is trying to save every drop of energy, it might lower the brightness or the sensitivity of the biometric sensors. This causes the “Fingerprint Hardware Not Available” error or makes the face unlock take five seconds instead of one.

I always check if the user has a third-party battery saver app installed as well.

1. Go to your phone Settings and tap on the Battery menu.
2. Ensure that Power Saving Mode or Super Power Saving Mode is turned off.
3. Test the fingerprint scanner while the phone is plugged into a charger to see if it performs better with full power.

Update the Funtouch OS Software

Vivo releases updates specifically to improve the accuracy of the in-display fingerprint sensors.

If you are running an old version of the software, you might be missing out on vital patches that fix known biometric bugs. I always check for system updates before I decide that a component is actually physically damaged.

1. Connect your phone to a stable Wi-Fi network.
2. Go to Settings and then tap on System Update.
3. If an update is available, download and install it immediately.
4. Let the phone finish the installation and wait for it to reach the home screen.
5. Test the biometrics again after the system has fully loaded all its components.

When to Seek Professional Help

If you have tried everything above and the sensor still does not respond, we might be looking at a hardware failure.

This happens if the screen was replaced with a low-quality part or if the internal flex cable has come loose after a hard impact. I have repaired units where the connector for the fingerprint module was slightly oxidized from humidity.

In these cases, I have to open the device and check the motherboard connections under a microscope.

Don’t try to force the phone open yourself if you are not experienced with delicate flex cables. I take pride in being patient with these repairs because one wrong move can kill the entire display.

If the device was recently submerged in water, the sensor is often the first thing to short out. I can usually clean the corrosion and get it working again, but sometimes the IC chip itself needs a replacement.

I will always give you an honest answer if the cost of the repair is higher than what the phone is worth.

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