The code *#899# is a secret (engineering or diagnostic) code used on some Android smartphones, especially OPPO, Realme, and OnePlus devices (since they share ColorOS / OxygenOS / RealmeUI roots).

When you dial *#899# in the phone dialer, it opens the Engineer Mode or Device Test Menu — a hidden diagnostic interface used by technicians and advanced users to test hardware components and system functions.

Here’s a list of common usages and functions found under *#899#:

🔧 Main Uses of *#899# Engineer Mode

1. Hardware Testing

   • Test the display (colors, touch, brightness)
   • Test vibration motor
   • Test speaker and receiver
   • Test microphone
   • Test camera (front/rear, focus, flash)
   • Test proximity and light sensors
   • Test gyroscope, accelerometer, compass
   • Test fingerprint sensor
   • Test SIM card and network functions

2. Software & System Diagnostics

   • Check software version and build number
   • Log system information
   • Check baseband version and radio info
   • Access bug reports and device logs

3. Network & Connectivity Tests

   • Wi-Fi test
   • Bluetooth test
   • GPS test
   • NFC test
   • Mobile network (LTE/5G) test

4. Battery & Power Management

   • Check battery health
   • Voltage, temperature, and charging status
   • Power consumption data

5. Device Calibration

   • Calibrate sensors (gyroscope, proximity, light)
   • Touch screen calibration

6. Debugging / Factory Verification

   • Perform factory hardware checks
   • View test history
   • Run automated diagnostic tests

⚠️ Important Notes:

• This menu is meant for service technicians; changing settings inside it may affect device performance or calibration.
• Not all options work or appear on every phone — it depends on the manufacturer and firmware version.
• Avoid modifying values unless you know what they do.