The situation when smartphone screen suddenly goes out immediately after bringing the handset to the ear, and then does not turn on when the device is moved away, is familiar to many users Android. This isn't just an annoyance: you don't see a call end button, you can't put a call on speakerphone, or you can't add a participant to a conference. In the worst case, while in your pocket, the phone continues to work with an active microphone, wasting battery power and recording extraneous sounds.
The main culprit for this behavior is almost always proximity sensor. This small sensor, located at the top of the display, usually next to the earpiece, uses infrared light to determine the distance to an object. Its task is to save energy and prevent accidental pressing of the cheek during a conversation. However, if the mechanism fails, the user finds himself hostage to a situation where control of the interface becomes impossible.
The reasons for the failure can be very different: from banal contamination of the protective glass to deep software errors in the firmware. Sometimes the problem lies in poor quality repairs, when the technician forgot to connect the cable or installed cheap glass that blocks the sensor. Let's look in detail at all possible scenarios and ways to eliminate them, from simple actions to complex engineering menus.
The principle of operation of the proximity sensor and its vulnerability
The technology of the sensor is quite simple, but requires precise calibration. The sensor emits an invisible infrared beam and analyzes its reflection. If the beam returns quickly, the system Android receives a signal that the object is closer than 2-3 centimeters and sends a command to turn off the backlight and touchscreen. When you remove the phone from your face, there is no reflection, and the screen should light up again.
Problems begin when optical sensor receives false data. This may be due to a physical obstacle or a software glitch that interprets the absence of a signal as the proximity of an object. In modern flagships, sensors are often hidden under the display or integrated into a dynamic system, which makes them more sensitive to build quality.
⚠️ Attention: Some smartphone models (for example, certain versions Xiaomi or Honor) have a sensor proximity can be software disabled by the manufacturer to reduce the cost of the design. In such cases, the screen goes dark based on a timer or accelerometer data, which often leads to false positives.
Understanding the physics of the process helps to understand why even a thin film or crack in the corner of the screen can be fatal to the function. The infrared beam is easily refracted or absorbed by foreign materials, creating the illusion of an obstacle to the system.
If you recently changed the glass or display, and the problem appeared immediately after that, with a 90% chance it is due to incompatibility of the spare part or a technician error during assembly.
Physical obstacles and contamination of the sensor
The most common but common reason is dirt. Greasy fingerprints, dust, cosmetics or drops of moisture in the area of the top edge of the smartphone can block operation infrared diode. The sensor cannot “pierce” the layer of contamination, so it believes that there is always an obstacle in front of it and keeps the screen turned off.
The second important factor is protective accessories. Cheap protective glasses often have a black frame around the perimeter, which can partially block the sensor's working area. This is especially true for models with cutouts (“notches”) or holes for the camera, where the space for electronics is extremely limited.
- 🧼 Thoroughly wipe the top of the screen with an alcohol wipe, paying special attention to the area above the speaker.
- 🛡️ Remove the protective glass or film and check the ringer operation without them - this is the best way diagnostics.
- 📱 Make sure that the case does not cover the upper end of the case, where additional sensors may be located.
Sometimes the problem lies in the case itself. If the phone has been hit or dropped, a microcrack in the display glass in the sensor area can scatter the beam. Visually, such a crack may be invisible, but for the optical system it will become an insurmountable wall.
Software failures and application conflicts
If the physical cleanliness of the device is beyond doubt, you should pay attention to the software part. The operating system Android controls the sensors through special drivers. A failure in the service Phone or system process System UI may result in the command to turn on the screen simply not being sent.
Often the culprits are third-party applications that intercept call control. Various smart dialers, spam blockers, or call recording applications may not process sensor signals correctly. They can forcefully turn off the screen and “forget” to turn it back on.
For diagnostics, try rebooting your smartphone in safe mode. In this state, only system applications are launched. If the screen behaves correctly in safe mode, then the problem is definitely in third-party software that needs to be identified and removed.
adb shell pm disable-user --user 0 com.example.bad.dialerIt is also worth checking for system updates. Manufacturers regularly release patches that correct the operation of hardware. Sometimes the problem is solved by simply updating the firmware to the latest available version, which fixes power management bugs.
How to enter safe mode?
Hold the power button on the screen. When the "Turn Off" icon appears, press and hold it for a few seconds. You will be prompted to enter Safe Mode. Confirm the action.
Calibrating the sensor through the engineering menu
When simple methods do not help, deep adjustment of the sensor is required. In smartphones based on processors MediaTek i Qualcomm there is a hidden engineering menu that allows manual calibration. This is the most effective way to correct the situation when the sensor “thinks” that the object is always nearby.
This menu is accessed through a special code in the phone application. However, be careful: changing unknown parameters may cause the device to become unstable. We are only interested in the section related to the proximity sensor (Proximity Sensor).
| Manufacturer / Chipset | Login code | Menu section | Action |
|---|---|---|---|
| Xiaomi / Redmi | ##6484## |
Proximity Sensor | Click Calibrate |
| Samsung | #0# |
Sensor > Proximity | View value (must be 0.0) |
| Huawei / Honor | ##2846579## |
ProjectMenu > | Check status |
| Universal (MTK) | ##3646633## |
Hardware Testing > Sensor | PS Calibration |
The calibration process usually looks like this: you cover the sensor with your hand (or bring the phone to your face), press the calibration button, then remove your hand and again press the button. The system remembers the minimum and maximum distance values. After this, you need to restart the device.
⚠️ Attention: On some new smartphone models, access to the engineering menu via USSD codes is blocked by the manufacturer. In this case, you will need superuser rights (Root) or a special PC application for calibration.
☑️ Calibration algorithm
Third-party applications for controlling the sensor
If the built-in system tools do not produce results, you can use the help of the developer community. In the store Google Play there are utilities designed specifically for testing and forcing control of sensors. They allow you to bypass system restrictions.
One of the popular solutions is an application Proximity Sensor Reset or analogues from independent developers. Such apps may reset the sensor cache or offer an alternative data processing algorithm. They are especially useful on older devices where manufacturer support has already ceased.
Another option is to use theme changers or launchers that have their own call handling settings. Sometimes replacing the standard dialer with a third-party one (for example, Truecaller or Simple Dialer) solves the problem, since the new application polls the sensors differently.
Third-party applications are a temporary solution. If the sensor is physically faulty, the software will only mask the problem, but will not eliminate it.
Radical measures: disabling the proximity sensor
In extreme cases, when the sensor is hardware faulty (burned out, the cable has come off), and replacing the screen or repair is impractical, the function can be disabled software. This will return you to the ability to see the screen during a call, but will require care not to press the buttons with your cheek.
Turning off often requires use ADB (Android Debug Bridge) via a computer. This allows you to make changes to system settings that are not available through the regular interface. The command disables sensor polling for the phone application.
adb shell settings put system proximity_on_call 0After entering the command, the screen will stop turning off during calls. You can end a call by pressing the button on the display. However, be aware of the risk: if the phone is in your pocket or bag, it may accidentally dial a number or turn on the voice recorder due to touching the fabric.
⚠️ Warning: Disabling the proximity sensor means that the screen will remain lit during the entire call. This will increase battery consumption and may cause the device to heat up during long conversations.
There are also applications that emulate the sensor using an accelerometer. They turn off the screen only when the phone is in a vertical position and not moving. This is a compromise option that works better than turning it off completely, but worse than a working IR sensor.
Risks of using emulators
Accelerometer-based emulators often make mistakes. If you simply put the phone on the table during a call, the screen may go dark because the device has detected a lack of movement.
Hardware repair and replacement of components
When software methods have been exhausted, and cleaning did not help, only hardware intervention remains. In most modern smartphones, the proximity sensor is part of the display module or the top cable (where the speaker and front camera are also located). Its separate replacement is not always possible.
A common cause of breakdown is oxidation of contacts due to moisture ingress. Even if the phone didn't sink, high humidity in the bathroom or condensation could cause corrosion of the sensor pad. At the service center, the board is washed with ultrasound, which often brings the sensor back to life.
- 🔍 Diagnostics with a multimeter will allow you to check the integrity of the sensor circuit.
- 🔌 Replacing the upper cable is the most common repair procedure in such cases.
- 📱 In rare cases, re-soldering of the sensor itself is required on the board, which requires micro-soldering.
It is worth noting that in budget models the quality of soldering and the components themselves are often lower. Sensors there fail more often than in flagships. If your device is several years old, perhaps the component’s resource has simply expired.
Before going to the service, be sure to back up your data. When replacing a cable or display, technicians are often forced to reset the phone settings or reflash it.
Why doesn’t the screen turn on when I remove the phone from my ear?
Most likely, the proximity sensor is stuck in the “object nearby” state. This may be caused by a software failure (a reboot will help) or physical contamination of the sensor. Try wiping the top of the screen.
Is it possible to permanently turn off a fading screen?
Yes, this can be done through the engineering menu (on some models) or using ADB commands. However, this is not recommended, as the risk of accidental clicks during a conversation increases.
Does the protective glass affect the operation of the sensor?
Yes, it does. If the glass has a solid black frame or is glued crookedly, it may block the infrared beam of the sensor. Try removing the glass to check.
Why did the screen go dark more often after updating Android?
The update could have changed the sensor sensitivity algorithms or contained an error in the drivers. Try a factory reset or rollback the update if possible.
I broke the screen and now the sensor is not working. Is this connected?
Yes, directly. In modern smartphones, the sensor is often built into the display matrix or located under glass. A crack in the speaker area is almost guaranteed to disrupt the operation of the sensor.