How to Access Engineer Mode in Spreadtrum Android Devices

In typical Android fashion, there's always a lot of stuff hidden under the hood and for valid reasons. Such is the case of Engineer Mode, sometimes also referred to as Service Mode, which is essentially a system app found in most android Devices. You can easily verify its existence in your phone by checking the installed System apps in your App Settings.
engineermode app
EngineerMode App in Settings
The purpose of Engineer Mode is as the name suggests to control certain aspects of device's hardware. From what I've gathered from my experience, it seems to act essentially as a bridge between the hardware and what is expected of that hardware in the practical sense. As such, it allows us to configure crucial aspects of the phone hardware not to mention run diagnostics.

Of particular interest is the Telephony area which allows us to configure how the phone communicates with the wireless networks of our providers, be it 2G, 3G or 4G/LTE and the various bands in use and the SIM card configuration (single or dual).
Telephony Section
 Other useful sections, are the connectivity (for Wi-Fi & Bluetooth config and testing), System Update and System Info (which also includes handy CPU and Memory usage monitors).
debug and logs
Debug & Log Section
hardware test
Hardware Test Section

Various phone manufacturers (OEMs) use different methods to hide in this mode. The most prevalent form is through the use of secret codes that are dialled via the phone's dialler app. As you might expect, the secret codes vary across the various OEMs and as such the codes might not work in some phones. For that one may have to rely on some third party apps. Fortunately, in my Spreadtrum powered device the secret code works as expected. The code is:


Just dial that and hopefully it should work. The app will be launched when you enter the last star (*) i.e. you won't have to press the call button. You can watch a video demo of this on YouTube here.

Getting the app to launch is the easy part, using it however requires some requisite knowledge.  Suffice to say, there's a lot of technical jargon in this mode that by saying I know very little of seems rather like an undue underestimation on my part. I suppose the targeted audience for this mode is the very "Engineers" it alludes to in its name. You know, the good guys at the service centres or repair shops.

I would therefore advice against changing anything here not unless you're relying on a reputable source of information. Otherwise you risk probably not damaging your device but most certainly making it unusable, that is, configuring it the wrong way so that it may not work as expected though the hardware is perfectly sound. You've been warned.