Android smartphones, including the OnePlus and Oppo have lot of interesting features for you to uncover, but to get the features you need to perform certain actions or access a particular menu on the phone using special code. You can use secret codes to access hardware diagnostic test on Oppo and OnePlus handsets. Here is how to run hardware diagnostic tests on OnePlus and Oppo handsets using service code.
Dialing the service code will enter your OnePlus and Oppo into service mode or engineer mode. In this mode, you can diagnose Wi-Fi problems, back and front camera issues, flashlight issues, battery charging, Bluetooth, Gyroscope, Proximity sensor, GPS, LCD brightness, see usage statistics of your phone, and many more, but with caution. Making unwanted changes are dangerous.
If you are an interested person, just dial the code
*#808# in the phone app, you can access hardware diagnostic mode or engineer mode on your OnePlus runs OxygenOS (OnePlus One, OnePlus 2, OnePlus X OnePlus 3/3T) and Oppo runs Color OS (Oppo R9, Oppo R7, etc.) handsets and then perform a variety of tests.
Note that, typing the code *#80X# will take you straight to individual tests (replace X with 1, 2, 3, etc.) For example:
*#801# - Engineering switch test mode
*#802# - Enter automatically engineering TTFF GPS test mode
*#803# - Enter engineering network test mode
*#804# - Automatic disconnect test mode
*#805# - Engineering Bluetooth test mode
*#806# - Engineering aging test mode
*#807# - Enter engineering test mode
*#808# - Enter manual engineering test mode
*#809# - Enter engineering echo test mode
*#888# - View hardware pcb version
*#900# - Test photograph RGB
Note that you can also create shortcut on the home screen for individual test using Nova Launcher or Action Launcher 3. If you are using any of these launcher, just go to Widgets > Activities > and then scroll down to Engineer Mode. Select required test mode (Source – XDA)