This guide provides a tested solution for the Diagnostic Trouble Code (DTC) U012100 - "Lost Communication With Anti-Lock Brake System (ABS) Control Module" that can appear in the VGSNAG3 (9G-Tronic) transmission control unit.
This error commonly occurs after deactivating the Forward Collision Warning (FCW) system in a Mercedes-Benz W205 Diesel, as the transmission is still expecting to receive certain CAN bus signals related to the FCW system. The following procedure corrects the transmission's variant coding to resolve this conflict.
Important Prerequisites
• Vehicle: This solution is confirmed for a Mercedes-Benz W205 Diesel with standard Forward Collision Warning (FCW). It is not for vehicles equipped with Distronic/DTR+.
• Tools: You must use Mercedes-Benz engineering software (e.g., Vediamo or DTS Monaco) with a compatible diagnostic interface (e.g., C4/C5/C6).
• Knowledge: This is an advanced procedure. You must be familiar with SCN/variant coding and understand the risks involved. Incorrect coding can lead to transmission malfunction.
Step-by-Step Procedure
1. Code Out FCW from Vehicle:
Connect to the vehicle. In the EIS_222 (Electronic Ignition Switch) and IC_222 (Instrument Cluster) modules, perform the necessary coding to fully deactivate the Forward Collision Warning system.
2. Connect to the VGSNAG3 Module:
Establish a connection directly with the transmission control unit (VGSNAG3).
3. Unlock the TCU:
Before you can write any changes, you must first send the command to unlock the VGSNAG3 module for variant coding.
4. Access Development Variant Coding:
Navigate to the variant coding section and select the correct domain to enable writing: "[000] Entwicklung Variantencodierung VGSNAG3 Reset Write".
5. Modify CAN Bits:
Locate the following two internal coding fragments in the list. As shown in the image below, you must change their values from the default to "INAKTIV".
(Here you should insert your vgsnag3.JPG image)
• CAN_1_Bit_06
• CAN_1_Bit_14
6. Write Coding & Hard Reset:
Write the new coding to the module. After the write process is complete and successful, perform a hard reset of the control unit. The most effective way is to disconnect the vehicle's battery for 5-10 minutes.
7. Final Check:
Reconnect the battery and clear all fault codes throughout the vehicle. Start the engine and then read the DTCs in the VGSNAG3 module again. The U012100 error should now be resolved.
Disclaimer
• Source of Information: This guide is based on information collected from public, open-source domains and is provided for educational purposes.
• User Responsibility: Modifying your vehicle's coding is an advanced procedure that carries significant risks. You, the user, assume all responsibility for any actions taken based on this guide. The authors of this post and the forum administration are not liable for any damage to your equipment or vehicle that may result from following these instructions. Proceed with caution.
This error commonly occurs after deactivating the Forward Collision Warning (FCW) system in a Mercedes-Benz W205 Diesel, as the transmission is still expecting to receive certain CAN bus signals related to the FCW system. The following procedure corrects the transmission's variant coding to resolve this conflict.
Important Prerequisites
• Vehicle: This solution is confirmed for a Mercedes-Benz W205 Diesel with standard Forward Collision Warning (FCW). It is not for vehicles equipped with Distronic/DTR+.
• Tools: You must use Mercedes-Benz engineering software (e.g., Vediamo or DTS Monaco) with a compatible diagnostic interface (e.g., C4/C5/C6).
• Knowledge: This is an advanced procedure. You must be familiar with SCN/variant coding and understand the risks involved. Incorrect coding can lead to transmission malfunction.
Step-by-Step Procedure
1. Code Out FCW from Vehicle:
Connect to the vehicle. In the EIS_222 (Electronic Ignition Switch) and IC_222 (Instrument Cluster) modules, perform the necessary coding to fully deactivate the Forward Collision Warning system.
2. Connect to the VGSNAG3 Module:
Establish a connection directly with the transmission control unit (VGSNAG3).
3. Unlock the TCU:
Before you can write any changes, you must first send the command to unlock the VGSNAG3 module for variant coding.
4. Access Development Variant Coding:
Navigate to the variant coding section and select the correct domain to enable writing: "[000] Entwicklung Variantencodierung VGSNAG3 Reset Write".
5. Modify CAN Bits:
Locate the following two internal coding fragments in the list. As shown in the image below, you must change their values from the default to "INAKTIV".
(Here you should insert your vgsnag3.JPG image)
• CAN_1_Bit_06
• CAN_1_Bit_14
6. Write Coding & Hard Reset:
Write the new coding to the module. After the write process is complete and successful, perform a hard reset of the control unit. The most effective way is to disconnect the vehicle's battery for 5-10 minutes.
7. Final Check:
Reconnect the battery and clear all fault codes throughout the vehicle. Start the engine and then read the DTCs in the VGSNAG3 module again. The U012100 error should now be resolved.
Disclaimer
• Source of Information: This guide is based on information collected from public, open-source domains and is provided for educational purposes.
• User Responsibility: Modifying your vehicle's coding is an advanced procedure that carries significant risks. You, the user, assume all responsibility for any actions taken based on this guide. The authors of this post and the forum administration are not liable for any damage to your equipment or vehicle that may result from following these instructions. Proceed with caution.
