(Solved) MB SD Connect C4 cannot access OBD port

MB SD Connect C4 diagnostic system can not only support Mercedes Benz Diagnostic function, it can also read faults from Benz SRS system.
MB SD Connect C4

According to customer’s feedback that he failed to access to the diagnostic OBD port when tried to read errors code from Benz SRS system. The system prompted an error message “check cable connection/turn ignition on”.

Possible reason:

The error lies on the SD Connect C4’s battery.


Solution from mbstartool:

1) Check and record your MB SD Connect C4 multiplexer battery
2) Hook up a digital multimeter to set it to the direct current
3) Get two t-pins and plug them into the OBD socket at PIN 5 and PIN17 position
4) Put your positive lead to PIN16 and negative lead to PIN5.
5) Write down the voltage on the digital multimeter
6) Check if the voltage you from PIN16 and PIN 5 is same in step 1.
7) Find the light green wire with a blue tracer band of PIN10 of the OBDII connector.
8) If the voltage differs in step 1 and step 6, the problem is probably with your battery.
9) If the battery is damaged or broken, please replace your battery.

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