Unlock Mercedes Coding: Why Standard J2534 is Your Best Bet

After a helpful tip, a solution for ignition detection has emerged. A small tool activates a checkbox in a window floating above the diagnostic assistance system, allowing users to tell the software whether the ignition is currently on or off. Here’s how it looks:

And since it was suggested that I write something about variant coding, here it is.

Software Tips for Mercedes Coding with J2534

When sourcing Xentry PassThru outside of official channels, you’ll quickly encounter multiple releases. Versions from 06/2020 onwards often have an online requirement, which can be cumbersome to bypass. If you’re not aiming to code the latest models and are comfortable working with vehicles produced up to mid or late 2019, opting for an older release can save you a lot of hassle. Given that the W169, for example, ceased production in 2012, and any lingering issues were addressed in the following years, the newest Xentry release isn’t always necessary for many tasks.

Ideally, when choosing an unofficial source, look for a pre-packaged complete setup with installation instructions. These are not too difficult to find.

Ready-made virtual machines (VMs) are also available, which you can simply launch to get started immediately. However, be cautious to find one specifically configured for Xentry PassThru. VMs designed for Xentry Diagnostics OpenShell often require extensive modifications within program folders, the registry, and configuration files before they function correctly. These VMs are generally intended for use with SDConnect, the official Mercedes multiplexer, or its Chinese counterparts, and therefore may not work seamlessly with affordable standard J2534 adapters right away.

Crucially, ensure you have Developer Mode enabled. This is essential to access the settings for advanced coding options.

For installation, it’s best to set up a separate, preferably older laptop (like a ThinkPad W510) with a clean Windows installation and no internet connection. This means the computer receives drivers and Windows updates once via the internet, and that’s it. Newer versions of Xentry have built-in spyware that attempts to transmit every vehicle modification to Mercedes servers. Additionally, there are automatic updaters and various tools that constantly try to communicate with Mercedes online. At best, the software might be remotely locked; at worst, you could face unexpected repercussions.

If you’ve opted for a virtual machine setup, you can use any computer as the host. Disconnecting the VM from the internet is straightforward: simply set the virtual network cable to “not connected” in the VM settings. USB passthrough for the J2534 adapter works flawlessly with free virtualization software like VirtualBox, making it a robust and cost-effective solution compared to more expensive proprietary tools.

Coding Procedures with a Standard J2543 Adapter

Disclaimer: You are solely responsible for any modifications you make to your vehicle. This guide is for informational purposes only, and I am not liable for any damage. Please be realistic about what coding can achieve; it won’t transform your standard AC into a THERMOTRONIC climate control system. However, simple yet useful customizations are indeed possible. Two classic examples are enabling the remaining fuel display and the date display in the instrument cluster. Here’s how to code these features:

1. Switch OFF the ignition and connect a battery charger to the vehicle battery to maintain voltage during coding.
2. Plug your J2534 adapter into the OBD2 port and connect it to your laptop.
3. Switch ON the ignition.
4. Start DAS (Diagnostic Assistance System) and navigate to the Main groups section.
5. Go to: Control units -> Information and Communication -> KIW Instrument cluster with maintenance interval display -> Diagnosis as per factory specifications -> Control unit adaptations -> Control unit adaptations (Variant coding).
6. Set Date in basic display to display.
7. Set Trip computer liters display to present.
8. Confirm twice with F3, then navigate back to the Instrument cluster area (simply go back page by page).
9. Go to: Actuations -> Control unit reset.
10. Confirm with F3 and wait until the instrument cluster restarts. Acknowledge success with F3.

The new functions should now be active. You may need to re-adjust your personal settings in the instrument cluster (e.g., mirror folding). Steps 9 and 10 are crucial; otherwise, nothing will happen after confirming the coding changes with F3 in step 8.

Result:

To hide the inactive Audio and Telephone menus (showing “—“) after a radio replacement:

(Steps 1 – 5 as above)

6. Set Menu level Audio to not present.
7. Set Menu level Telephone to not present.

(Steps 8 – 10 as above)

Result:

The telephone and volume buttons will continue to function as before. However, by removing the “Audio” and “Telephone” menus, you lose the ability to send commands to the radio using the left “arrow up” and “arrow down” buttons, as these are used by the instrument cluster for scrolling in all other menus.

It’s outrageous that some people are brazen enough to charge €150+ for these few clicks without any guarantee of success. Words fail me.

Other coding options I’ve found so far:

• For the air conditioning, you can disable the automatic recirculation control, allowing the recirculation function to remain permanently on until manually switched off. Unfortunately, it always defaults to off when the vehicle is started, and as far as I know, this cannot be changed.
• In the SAM (Signal Acquisition Module), you can reconfigure your fog lights to function as cornering lights if desired.

If there’s interest, I can provide the steps for these procedures as well. The process is always similar to the instrument cluster coding. For those hoping to quickly enable CarPlay in an old Comand NTG 2.5 or retrofit DAB to an Audio 20, disappointment awaits. Neither of these is possible through coding alone. If the necessary hardware isn’t present, coding won’t magically add it.