This module must be coded with Mercedes Star Diagnostics after installation.

SAM stands for Signal Acquisition Module. A SAM module (also called Signal Actuation Module) receives data from sensors, switches, and controllers, and can send data, actuate (activate) components and monitor systems. Mercedes-Benz has been using SAM modules since the mid-90s.

Symptoms of a defective Mercedes SAM unit

This is a list of a few possible SAM related problems. All systems on a Mercedes-Benz are controlled via CAN  Bus and SAM units, and any issue that you may experience could very well be due to a defective SAM unit.  SAM units don’t frequently fail unless there is water intrusion or other problems.

Here are a few problems caused by a bad SAM unit:

• Fuel Level / Gauge not working – The sending unit installed in the gas tank records the fuel level. In cars without CAN / SAM, the signal is sent directly to the instrument cluster via two wires. On Mercedes-Benz, the signal has to be sent to the rear SAM since it is the closest unit in the Controller Are Network. From here the fuel level data can be sent to the instrument cluster or the engine control unit for computing remaining distance based on fuel level.
• Lights not working – We have seen many Mercedes-Benz where one or a few lights don’t work. It can be that the left or right low beams, fog lights or turn signals may not work. You should always avoid splicing wires to get power for aftermarket HID lights, alarm or connecting a trailer hitch.
• Fuse Keeps Blowing – If you have a fuse that keeps on blowing, it is possible that the SAM module is defective and needs to be replaced.
• Poor key fob / keyless entry range – The key lock and unlock signal for the doors is transmitted via the rear antenna. The antenna is connected to the rear SAM module and a short in the wiring can cause damage to the SAM unit. If this is your dilemma, you may notice a blown antenna fuse.  Especially if you replace the fuse and it keeps on blowing. Don’t use a higher ampere rating fuse to try to fix this problem.
• Battery Drain –  A defective SAM module can cause battery drain when a Mercedes-Benz is parked overnight or for several days. Other possibilities should be eliminated such as a defective audio gateway unit or a bad power seat motor.
• Taillights staying on – If one or both of your tail lights stay on all the time it is possible that your rear SAM unit is defective. Other symptoms of a bad rear SAM include doors showing open all time, even when the doors are closed.
• Center Dashboard Buttons don’t work – Currently, we are working on an S-Class in which all the center buttons ( hazard light, head restraint, AIRMatic switch etc.) don’t work. In this case, we are not getting any communication with the module which most likely is an issue with the SAM unit.
• Mercedes Blowing Only Cold Air – This problem could be caused by a defective front SAM module. Before you replace the front SAM module, also check (changeover/duo valve) water valve first.

SAM Module Explained

Think of  SAM as the router in your home. All your devices network printers, phones, computers (switches, window motors, sensors, etc) communicate with each other via your router. If you hit print on your PC, the data (signal) gets sends to your network printer via the wireless router (SAM unit). You may also hear the term CAN Bus which stands for Controller Area Network. Think of  CAN Bus as that ethernet cables and wi-fi that make up your home network communication possible.