WIS 54.21 Control Units/Modules

SAM (Signal Acquisition Module)

A SAM (Signal Acquisition Module) functions much as a network router does on a computer or communications network. It monitors input from various switches, controls, monitoring devices, and warning systems. When you push a button on, for example, your dashboard, the signal goes through a SAM before the device you are controlling responds. If there is something wrong with the device you are trying to operate, you will likely then get a warning, delivered through the SAM to the CAN (Controller Area Network) bus.

Fault Error Codes/Diagnostic Trouble Codes (DTC)

DTC Structure

DTC Example

P0420 Catalyst System Efficiency Below Threshold (Bank 1)

• 1st digit: (P) Indicates which system reported the fault.
  • B = Body,
  • C = Chassis,
  • P = Powertrain,
  • U = Network eg CAN
• 2nd digit (0) Indicated type of fault code.
  • 0 = Standardized eg OBD Code
  • 1 = Manufacturer Code
• 3rd digit (4) Indicated the assembly where the fault occurred.
  • 1 = Fuel and airflow monitoring
  • 2 = Injection nozzles
  • 3 = Ignition system and combustion misfiring
  • 4 = Additional systems for emissions reduction
  • 5 = Idle and vehicle speed
  • 6 = Onboard computer and other outputs
  • 7 = Transmission
  • 8 = Transmission
• 4th digit (20) Indicated faulty component and type of fault.

List of DTC

Downloadable pdf files.

http://www.benzworld.org/forums/w220-s-class/1639927-guide-mercedes-benz-vehicle-data-card.html