The situation when the smartphone screen remains active during a phone call is one of the most common problems of owners of devices based on Android. This is not just an annoying little thing, but a serious inconvenience: the user accidentally presses the volume buttons, starts recording a conversation, opens a menu, or even ends a call. In the worst case, if the phone is in your pocket, the active screen can unlock and “pocket dial” numbers from the contact list.
The correct operation of the smartphone is based on proximity sensor, which should automatically turn off the display when you bring the phone to your ear, and turn it back on when you end the call. However, in modern models, especially with frameless displays and camera cutouts, this mechanism often fails. The reason may be either software errors or physical obstacles, such as protective glass or a case blocking the touch zone.
This article examines in detail algorithms for diagnosing and troubleshooting screen lock problems. We will look at ways to check the functionality of sensors through the engineering menu, settings for special features that often conflict with the basic functions of the phone, as well as methods of forced blocking through third-party utilities. Understanding the principles of operation of these mechanisms will allow you to solve the problem yourself without contacting a service center.
The principle of operation of the proximity sensor and the causes of failures
The main element responsible for blanking the screen is the infrared sensor located in the upper part of the smartphone body. It emits an invisible beam and reads its reflection from the object. When you hold the phone up to your head, the beam is reflected and the system is notified to turn off the touchscreen and display to save power and prevent false clicks. In modern flagships, this role is sometimes performed by a virtual sensor, working in conjunction with the camera and artificial intelligence algorithms.
If the screen does not go dark, this most often indicates that the sensor is “blind” or receiving incorrect data. A common cause is poor-quality protective glass, which has a frame that is too thick or a black stripe at the top that overlaps the sensor area. Even a microscopic layer of dust or grease on the front panel in the speaker area can disrupt the passage of the infrared signal.
It is also worth considering the design features of specific models. In some devices, for example, from Xiaomi or Honor, the sensor may be shifted to an unusual place due to the placement of the front camera. Users often do not realize that this particular area should remain clean. In addition, software glitches in the firmware can lead to the system simply ignoring sensor readings, considering them erroneous.
Before starting diagnostics, be sure to wipe the top of the screen with microfiber. Sometimes the problem is solved by simply cleaning the area above the speaker from dirt.
It is important to understand the difference between a complete malfunction of the sensor and its temporary incorrect operation. If the screen goes blank but comes back on immediately, there may be a problem with the calibration or a third-party app that is taking over power control. In the case when the display does not go off at all, we are talking about physical blocking of the sensor or its hardware failure.
Diagnostics and testing of sensors through the engineering menu
The first step in solving the problem should be to check the functionality of the sensor itself. In the operating system Android there is a hidden engineering menu that allows you to test all hardware components of the device without installing additional software. This menu is accessed through the standard "Phone" application by entering special combinations of characters.
For most devices based on chipsets MediaTek i Samsung the universal code is ##6484## or #0#. After entering the last digit, the menu will open automatically. You need to find the item associated with the proximity sensor (usually called Proximity Sensor or PS). In the window that opens, you will see the current value of the distance to the object.
☑️ Checking the proximity sensor
When performing the test, place your palm on the top of the screen. If the sensor is working properly, the numbers on the screen will change (usually from the maximum value to zero or vice versa), and the screen may go dark. If the values do not change even though you cover the sensor completely, the problem is hardware or driver related. In this case, software settings are unlikely to help.
⚠️ Attention: Combinations for entering the engineering menu may differ depending on the manufacturer and firmware version. If standard codes do not work, look for a specific combination for your model on the Internet or use applications like Phone Info SAM.
Some manufacturers, such as Google or OnePlus, have hidden access to the classic engineering menu in the latest versions. Android. In this case, it is recommended to install a free application from the store Google Play, for example, Test Your Android or Phone Tester. These utilities provide similar functionality for checking the status of all sensors in a convenient graphical interface.
Setting accessibility features and gestures
Often the reason that the screen does not lock during a conversation is the accessibility settings. The operating system offers features for people with disabilities that may conflict with the phone's standard behavior. In particular, the “Hold screen during a call” option or similar gesture settings can force the display to remain active.
To eliminate this factor, you need to go to the settings section Accessibility (Accessibility). Please review the list of included services carefully. If you see gestures, screen magnification, or voice apps active, try disabling them temporarily and making a test call. Sometimes even the built-in "Short Commands" function can interfere with the operation of the sensor.
- 📱 Check the section
Improving visibilityand disable the option to remove animations if it is active. - 🚫 Disable the "Quick Press" or "No-touch Control" function if they are enabled.
- 🔍 In the screen settings, find the "Prevent accidental taps" item and make sure it is activated.
Another common reason is “no-touch gestures”, which are found in many shells, such as MIUI or One UI. The feature that allows you to answer a call by waving your hand or turning the device over may not process data from the gyroscope and proximity sensor correctly. Try disabling all gesture controls in system settings and check if the problem goes away.
Why do gestures affect the sensor?
Android's priority system may prioritize gesture processing over the proximity sensor signal. If the gesture recognition algorithm freezes, it does not transmit a command to lock the screen, assuming that the user is interacting with the phone remotely.
It is also worth paying attention to the settings of the Phone application itself. Some launchers and dialers have their own blocking settings. Go to the settings of the application Google Phone or your manufacturer's standard dialer, find the "Incoming calls" section and check if there is an option "Keep the screen on" or similar call behavior settings.
Problems with protective glasses and cases
Physical accessories are the culprit of problems with the proximity sensor in more than 50% of cases. Manufacturers of protective glass do not always take into account the exact location of sensors in specific smartphone models. The black camouflage frame around the glass may be wider than necessary and block the infrared emitter.
This is especially common in budget universal glasses or accessories from little-known brands. Even if the glass does not visually cover the sensor, its adhesive layer or thickness can distort the signal. Try carefully removing the protective glass and making a call. If the screen starts to go dark correctly, the problem is solved - you need to replace the accessory with a better one or with a cutout for the sensor.
| Type of accessory | Probability of problem | Recommendation |
|---|---|---|
| Cheap universal glass | High (80%) | Replace with the original one or with a precise cutout |
| Thick book case | Medium (40%) | Check the magnetic hall sensor |
| Hydrogel film | Low (10%) | Usually no effect, check the sticker |
| No protection | Minimum (5%) | Problem in software or hardware |
Flip cases with a magnetic clasp use a Hall sensor to detect the opening and closing of the lid. If the magnet in the case is too strong or poorly positioned, it may interfere with other sensors on your smartphone, including the proximity sensor. Try removing the case completely and testing the operation of the phone in a “bare” form.
If removing the protective glass solved the problem, do not use this accessory again. Look for models marked "Full Coverage" with exact cutouts for your model's sensors.
In rare cases, the problem may be caused by a sticker on the screen that they forgot to remove when purchasing, or glue residue from the previous glass. Carefully inspect the top edge of the display under a bright light. Any extraneous inclusion in this zone may cause the locking system to operate incorrectly.
Resetting settings and updating software
If hardware reasons are excluded, and the accessibility settings did not help, it is likely that software garbage has accumulated in the system or a driver failure has occurred. The first step is to check for operating system updates. Developers often release patches that correct errors in working with sensors in new versions. Android.
Go to the menu Settings → System → System update and click the check for updates button. If a new version is available, install it. Before updating, be sure to create a backup copy of important data, as the process may take a long time and requires a reboot of the device.
⚠️ Attention: Menu interfaces and item names may differ depending on the version of Android and the manufacturer's shell (MIUI, OneUI, ColorOS). If you do not find the specified path, use the search in the settings by entering the word “Update”.
A more radical, but effective method is to reset the phone to factory settings. This action will remove all installed applications and user data, returning the device to its out-of-the-box state. Often it is third-party applications that have rights to cover the screen or control calls that cause conflict. Before resetting, make sure that all contacts and files are saved in the cloud.
The reset procedure is performed through the menu Settings → Advanced settings → Recovery and reset → Reset settings. Once the process is complete, the phone will reboot and you will need to set up your Google account again. If, after a clean start of the system, the problem with the screen lock disappeared, then the culprit was one of the previously installed applications.
Use of third-party applications for blocking
In cases where the standard proximity sensor is physically faulty, and replacement There are no plans for a screen, you can use a software crutch. There are a number of applications in the store Google Playthat forcefully lock the screen when starting a conversation, ignoring the readings of the standard sensor. They use data about the state of the telephone line to activate the blocking.
One of the popular solutions is an application Proximity Sensor Reset or analogues, such as Screen Off During Call. These utilities work in the background and monitor the call status. As soon as the call starts, the application sends a command to turn off the display. However, it is worth considering that such apps require permanent permissions to access the phone and over other applications, which can slightly increase battery consumption.
When installing such software, carefully read the reviews and check the permissions. Some applications may contain intrusive advertising or collect unnecessary data. Choose solutions with high ratings and a large number of installations. After setting up, be sure to test the operation of the application by making a call to the answering machine number.
Risks of using third-party blockers
Such applications may conflict with system functions, for example, interfere with the operation of speakerphones or Bluetooth headsets. Use them only as a temporary solution until the sensor is repaired.
It is also worth mentioning the possibility of using custom firmware for advanced users. The community XDA Developers often releases modified versions of software that fix sensor driver errors that are relevant for specific smartphone models. However, flashing the device requires special knowledge and carries the risk of turning the phone into a “brick.”
Frequently asked questions about screen locking (FAQ)
Why does the screen go blank, but the phone immediately unlocks?
This is a classic sign of “bouncing” of the sensor contacts or incorrect calibration. The sensor detects the approach, turns off the screen, but due to interference or driver failure, it immediately sends a signal to remove the object. Try calibrating the sensor through the engineering menu or resetting your phone.
Is it possible to disable the proximity sensor completely?
Using standard Android tools, you cannot disable only the proximity sensor, since it is a system component. However, you can use blocker applications that ignore its readings, or get root access to edit system files, which is not recommended for ordinary users.
Does the power saving mode affect the operation of the sensor?
In some shells, an aggressive power saving mode can limit the frequency of sensor polling to save battery. This results in delays in screen response. Try disabling the power saving mode and check the phone's operation in normal mode.
What to do if, after replacing the screen, the sensor stops working?
Most likely, during the replacement, a non-original display module was used without a working sensor, or the technician forgot to connect the sensor cable or apply thermal paste/gasket. You need to contact the service to check the quality of installation of components.
Does rebooting the phone help in this situation?
Rebooting can temporarily solve the problem if it is caused by a freeze in the system process responsible for processing sensor signals. However, if the problem recurs regularly, a more in-depth diagnosis of the settings or hardware is required.