My car had no sound. Still does, but came on for a few seconds, then went off before Theft message on screen. This mission started a few weeks ago. I didn't know which component was faulty. Tried replacing each module and jumped MOST fiber at each connection. Still no sound. Tried using Diag mode (Call End/1/# I think all together). Wouldn't run a wake up test. Got a scanner and tried to run a wake up Test and it stated there was an Internal Error on the HU from my Autel. Also stated Telematics issue B15D814 - Break in Audio muting connection (open circuit or grounded). I spent hours mapping the wires so hope this helps someone. Got a replacement radio - programmed it to old OE radio and Fault Scan says theft protection is activated and a PIN mismatch. Says Theft Protect on screen now. I did hear sound come on for a second or so. Cluster says Audo off. I don't know OE radio PIN. I assume I need PIN for old radio to be overwritten on new radio and theft protection disabled or operational. Any advice is greatly appreciated. Can someone run a PIN lookup?

Here is the radio layout for my car and assume other W204 if you have similar connections on back of radio. Hope this helps someone else. I spent many hours mapping each wire out and where it went and check continuity. Tip - I used two sewing needles in pins on connectors to check continuity with multimeter. Helped out tremendously to test cables and find them. Also tested if they were broken or grounded somewhere.

Radio
White - Dual Antenna (Farka)
Green - Nav (LVDS) - grey in glove box
Pink - Armrest USB
Grey - screen (Blue on back of Screen)
Yellow - BT module Overhead light (Farka)

Radio Harness
Black Connector in harness (small)
All connect back to Nav Connector
clear, brown, yellow/tan (2 pairs)

White Connector in harness (small)
Clear, black - goes to Telematics unit behind seats in trunk
Clear, Orange, Tan, green - goes to MIC above Overhead light in top of rear mirror
black, black/yellow - in Nav Connector

Center Plug area (pins) in harness
Red thick - power
Brown thick ground
Brown/Red, Brown - Can Bus
Black/Blue - wake up

Media interface Module
Blue LVDS / Metal connector - armrest MMI connector (aux)
MOST fiber/power opposite side

MOST Fiber routing in order
Radio -1 (Master)
Amp (Driver side trunk) - 2
Sirus Module (center trunk behind seats) - 3
Media Interface module - glovebox - 4
Back to radio (Loop)

Telematics
No fiber - attaches to radio with black/clear wires
Connector - no idea where they went
Couple Antenna connectors (Farka)

Amp
Drivers side trunk
Fiber
Big Connector - Speaker wires (Twisted), power/ground, wake up (black/blue), Yellow/black (unknown)

Sirus Module
Power/Fiber
Blue Antenna (Farka)

MY Radio Info:
OE Radio with Two issues (MOST / Telematics Audio Muting)
523 PA1138D0996285 2
Used Radio
523 PA1138D0806911 6


Front (NTG 4.5)

Back - label connections

OE Radio

New Used Radio

 

Try this,

PA1138D0806911
PIN V6V4JMX8Y4YHBQN4QF9965V92