The Peugeot 308 is packed with advanced electronics, but many of its most useful features are hidden away in the "secret menu" or Service Mode. Whether you are driving the classic first-generation T7, the popular T9, or the latest hybrid models, these hidden screens allow you to check battery health, view real-time engine data, and troubleshoot sensor issues without a diagnostic tool. Accessing the Peugeot 308 Secret Menu

The method for entering the secret menu depends entirely on which infotainment system your Peugeot 308 uses. For the Smeg and Smeg+ Systems (T9 Model 2013-2017)

The Smeg system is the most common interface for the second-generation 308. To access the hidden service data: Turn on the ignition or start the engine.

Press and hold the "SRC" (Source) button or the "Settings" icon for approximately 5 to 10 seconds. A "System Information" screen will appear.

From here, you can see the firmware version, Bluetooth version, and map data.

To go deeper into the technical "Cheat Codes," hold the "Music" or "Media" button. A keypad will appear where you can enter specific codes like "BTK" or "SPY" to view system logs and CPU usage. For the NAC Infotainment (Post-2017 Models)

Newer Peugeot 308s use the NAC system. Accessing the hidden menu here is slightly different: Press the "Music" button on the piano keys for 5 seconds.

Release and immediately press the "Nav" button for another 5 seconds.

A screen labeled "Expert Mode" or "Engineering Menu" should appear. This menu provides detailed GPS satellite data, internal temperature of the head unit, and voltage readings. What Can You Do in the Secret Menu?

⭐ Monitor Real-Time Battery VoltageOne of the most practical uses for the secret menu is checking the battery’s health. If your Stop-Start system isn't working, it’s often because the voltage is too low. The hidden menu shows the exact voltage the alternator is providing.

Check Firmware VersionsBefore attempting to update your maps or CarPlay/Android Auto settings, you need to know your exact firmware build. The secret menu provides the long-form version number (e.g., 5.43.A.R2) that isn't visible in standard settings.

GPS Signal TroubleshootingIf your navigation is acting up, the hidden menu allows you to see how many satellites your 308 is currently tracking. This helps determine if the issue is a software glitch or a physical antenna failure.

System Logs and ErrorsThe "SPY" logs found in the Smeg system record every minor electronic hiccup. While mostly used by technicians, it can help you identify if a specific module (like the parking sensors or reversing camera) is intermittently failing. Safety Warning

While exploring the secret menu is generally safe, you should avoid changing any "Config" settings or "Rebooting" the system while the vehicle is in motion. Some "Cheat Codes" can factory reset your navigation, wiping your saved addresses and paired phones. Only use these menus to observe data unless you are an experienced DIY mechanic.

If you are trying to reset the "Service Due" light, you do not need the secret menu. Simply hold the "000" or "Set" button on the instrument cluster while turning on the ignition, and wait for the countdown to hit zero.

To provide you with the exact codes or steps for your specific car, could you tell me: The year of your Peugeot 308?

The type of screen it has (Small monochrome, early touchscreen, or the new i-Cockpit)?

Knowing these details will allow me to give you a list of specific "Cheat Codes" for your infotainment system.

The Peugeot 308 (specifically models with the infotainment systems) features an "Engineering Mode" or secret menu used by technicians to view system diagnostics, GPS signal strength, and firmware versions. Accessing these menus typically requires a combination of button presses and a passcode. Mittns Peugeot Forum How to Access the Secret Menus

Access methods vary depending on your car's generation and head unit type: NAC Systems (Modern i-Cockpit, 2017+): Press and hold the

button (or the gear icon/cog) for approximately 5–10 seconds.

A keyboard will appear asking for a code. Common codes include: : Basic system info. : Privacy settings and TSM information.

: Often used as a confirmation code after entering other commands. SMEG Systems (Older 308 models, approx. 2013–2017): Press and hold the button or the button for 5 seconds until the screen changes.

This menu typically shows software versions, GPS satellite data, and hardware temperatures. RNEG Systems (First-gen 308): Turn on the ignition and wait for the system to boot. Press and hold the Once the first menu appears, press again while simultaneously holding buttons 1, 2, and 3 Key Features in the Engineering Menu System Diagnostics:

View real-time GPS signal strength and the number of connected satellites. Version Checks:

Verify the exact firmware and mapping versions currently installed on your vehicle. System Reboot:

Manually force the infotainment unit to restart if it becomes unresponsive. Demo Mode:

A mode used by dealerships to cycle through features for display. Peugeot France Peugeot 308 Overview & Tech Review

The current Peugeot 308 is noted for its premium shift, aiming to compete with the Volkswagen Golf and Mercedes A-Class. All-new Peugeot 308 GT full review 3 Dec 2022 —

To access the secret engineering or "Expert Mode" menu on a Peugeot 308 (typically models with the SMEG or NAC infotainment systems), you can follow these steps to reveal hidden diagnostic data and system settings.  How to Access the Hidden Menu 

Preparation: Turn on the ignition or start the engine to power the infotainment system.

The Trigger: Press and hold the Music/Media piano key (or the toggle switch) for about 6 seconds.

Authentication: A keyboard will pop up on the touchscreen asking for a four-digit code. Common Codes:

1111: Enters "Spy Mode" or "Expert Mode," which displays various system logs, hardware versions, and software details.

1142: Can be used in conjunction with other codes to check ATB status (connected services).

1122: Often used to view specific diagnostic screens after an initial code has been entered.  Available Information  Once inside, the menu typically allows you to view:  System Information: Exact firmware and map versions.

Diagnostic Logs: "Spy logs" that record system errors or performance.

GPS/Connection Data: Real-time satellite reception and 3.5G/4G connection status.

Hardware Status: Temperatures and voltages for various internal components.  Modern i-Cockpit Customization 

For the newest Peugeot 308 models (2021+), much of the "hidden" feel is now integrated into i-Toggles. You can customize these digital sliders by pressing and holding the central screen to enter a layout mode where you can drag and drop functions for quick access.