MPPS V21 - Mercedes W211 E220 CDI EDC16C2 - reads fine, "Security access denied" on write

Hi all,


I'm stuck trying to write a modified file to a Mercedes W211 E220 CDI over OBD and I've run out of ideas. Any input appreciated.


Vehicle / ECU


Mercedes W211 E220 CDI, 2005, OM646, 150hp<br>Bosch EDC16C2 (MPPS reports: BOSCH EDC16C/C2-7.x MPC)<br>Mercedes Hardware ID : A 6461535691<br>Mercedes HW / SW : 4302 / 1105<br>Bosch program number : 1037369286 P321/C49<br>Bosch calibration : 1037376828 P321/C49<br>Programming date : 21.01.04<br>

Tool


MPPS V21, Sw.Ver. 21.0.1.3, Amt Flash 1.09.03<br>Windows 10 64-bit<br>NOTE: hardware is a V18 cable running the V21 software<br>

What works


ECU ID and Read both work fine, every time. Ecu Found On Can. I have a good full read of the original.


What fails


Write always ends with "Security access denied", 0% progress, nothing is written.


In the ECU Data panel MPPS reports:


Checksums found 3 corrected 0<br>Power status High / Power percentage 86%<br>

and in the Comments box:


Data Area Read Only<br>

What I already tried

• Both ECU entries in the list: E220 2.2 CDI (W211) EDC16C2/3/4 and EDC16C31 — same error on both
• Speed: Medium and Slow (Recovery)
• Data Options: Data only and Full (where possible)
• Full ignition cycle, key out, wait, ignition position 2, immediate write
• Battery charger connected, voltage 12.2–12.3V
• Checksum corrected in the file beforehand

File analysis


The car was previously tuned by someone else. I compared the tuned file against the original byte by byte:

• The program area (0x00000–0x7FFFF) is byte-identical to stock — the previous tuner changed nothing there, so no custom lock was added to the security routine
• All changes are in the data blocks (maps, plus the DTC tables zeroed for EGR/DPF off)
• The previous tuner wrote a text tag Tag:YGRemaps at 0x0BFF50, in an area that is empty (FF) in the original
• I restored that tag area back to stock and tried again — same error

Relevant detail


The same MPPS, same laptop, same cable wrote a BMW EDC16C31 file successfully about a week ago, no issues at all. So the tool itself works.


Question


Is Data Area Read Only + Security access denied a known limitation of MPPS on Mercedes EDC16C2, or is something else going on?


Has anyone actually written a Mercedes EDC16C2 over OBD with MPPS? If yes, which software version?


Can a V18 cable running V21 software cause this, or does it make no difference?


If OBD really isn't possible here, is bench with the MPPS bench cable enough for this ECU, or does it have to be BDM?


Thanks