The Peugeot 308 contains several "hidden" or expert-level menus that allow you to check system health, verify GPS data, and even reset service alerts without a mechanic's tool. 1. The SMEG/Infotainment Hidden Menu

While the secret menu is useful for diagnostics, Peugeot also offers standard customization features for safer everyday use: Peugeot 308 Secret Menu

The method for entering the hidden menu depends on your specific infotainment system, such as the SMEG or WipNav units. SMEG & SMEG+ Systems (Common in 2013–2017 models): Turn on the ignition and wait for the system to boot up.

4.3. Electrical Status

The menu often provides real-time voltage readings from the battery. This is a more accurate diagnostic tool for parasitic drain or alternator issues than the dashboard battery light, which is binary (on/off).

Before exploring the secret menu, keep in mind:

3.1. The Audio Button Method (Diagnostic Mode)

This is the most reliable method for accessing diagnostic information on the T9 platform.