Do you know if this would be the same procedure for the X164? They share many features. I too have replaced the left rear actuator and had the SAM scanned. The scan shows no code but neither the old nor new actuator locks or unlocks. I also have keyless go. Am I right to assume that pins 21 and 22 supply voltage to the motor and just reverse polarity via the SAM?

 

Why do you think the problem is the rear SAM?

Nine times out of ten the spring is broken in the respective door module.

 

Thanks for the reply on this old thread.
I had tried replacing the spring several years ago. It made it no better or worse. At that time the unlocking function would work but not the lock function. Eventually the unlock function also stopped working. I bought a new Genuine Mercedes door lock actuator from AutohausAZ and it does not lock or unlock either. From what I have read both in the forums and from the part description, the front SAM controls the left rear actuator and the rear SAM controls the other 3 doors. I still have the door panel off so I am going to probe the wires to see if I get any 12v pulse when I try the lock or unlock. I don't have a wiring diagram or know the color codes for the wires so I will probe them all, one at a time. I do know some wires are for the motor, some are for the chrome part of the exterior handle (keyless go) and some for the button on the exterior door handle.

 

Open the left rear door and locate connector X35/3 and remove rubber casing and see if any wires are broken, namely Violet/Blk and or White wires.

 

I brought the car to my local independent shop. He scanned the front and rear SAMs, no errors. I then bought a $10 test probe from Harbor Freight that detects "no signal", +12v and Ground. It has a single LED that is off when no signal is present. Lights up Red when 12V is present and lights up Green when ground is present. I found the Violet/Black and the White wires with the door panel removed, and was able to pierce the wires with the probe and actuate the lock/unlock button. I tested this on both the Violet/Black and on the white wire. Without pressing Lock/unlock, the wires show 'open'. Each time the lock/unlock was pressed I got a one second pulse but it was always ground. I never got a +12v signal from either wire with either lock or unlock. I believe my SAM is bad. It is just a PITA to get to and $$$ to replace and then reprogram. My plan is to buy the part, bring the car to the mechanic so he can backup my existing SAM and replace with the new SAM and restore the program features to the new unit. Looks like I'll be be paying him to do the labor.
Here's the tool, seems pretty handy. https://www.harborfreight.com/comput...obe-63597.html