DIY:REAR SAM low cost repairing.


May 8, 2009
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East coast, Athens -Greece
Your Mercedes
MB w203,Getz 1.6,Elan+2,2Racing minis

Few months ago, during a battery replace, my rear SAM gone off, (was an early 0025459701, which are not in production any more). I replace it with the equivalent newer 2035453401 (or 2095450101), in the official stealers + star programming bla-bla, ... and 350€-400€ the cost. Also I bought a used one [0025457801 (it covers a lot of MB models incl.. w203- is similar to 0025459701), for 50€ for reserve]. Finally, got from a friendly workshop, a blown .... 701one for free, to practice myself.

Then I got mine bad one, and when I had some spare time, I tried playing, to find a cheaper solution for this common w203 failure. Here are the results:

A: solution
SYMPTOMS( After battery replaced, or charged, or jump up...)
Faulty display visit workshop in the cluster panel
No fuel gauge indicator
No turning signals
No wipers
No reverse lights
No boot opening
and some others that rear SAM controls

Some guys wrote in the forum that, the SAM's programming is getting lost only , and with a SAM's reprogramming in star diagn. everything is ok again. But unfortunately it seems no true, because all the cases I discuss with, MB official mechanic, and some other MBindies, all replaced the rear SAM, us I did.

By AUTO FIX (Senior member)

This sam problem, as you have shown, is nothing more than a software issue. There is no hardware fault. It is actually possible to program the old MCU with a “virgin” dump and it works fine. This is basically what codecard are selling.

This situation is true of a lot of modules in Mercedes and other makes. Imagine having to buy a new PC every time windows crashes.
In some cases the boot sector is corrupt so there is no way to flash serially but sometimes it is possible. When the boot sector is damaged the only way is on the bench with a programmer. A collection of virgin dumps and the knowledge of how to manipulate existing ones is all that is required.
Around the world there is a small community of techs who share solutions for these type of problems, especially on common problems, eg EIS’s.

Some modern automotive technicians have a range of eeprom programmers, hot air stations etc in their arsenal of tools. This allows tuned in independents to be far more efficient (cheaper) than dealers as the dealers will never do this level of work. In reality Mercedes should solve this problem themselves.


The affected part when this happened, is a 64pin processor inside the SAM. Motorola's MC68HC908AZ60 2J74Y processor. (pdf *)
If it is the 2035453401 and newer SAM, you are lucky just unclick the rear cover and the chip is visual in the side(ph:A1), ready to replace it.

Instead, the early SAMs like 0025459701, 0025457801 is a headache. When you open the cover - surprise - you find the opposite side of electronic parts(ph:294), so processor is underneath, and you have to dismalt all the SAM, and desolder the whole base to reach the chip. But don't worry, just do a cut (19x5cm) in the plastic base where the label is (ph:293), with care. [You have more than 1cm underneath clearance all the way, except in the red arrow (ph:293 ), attention!], and voila, the chip is in the centre, ready to proceed.

Remove keys
Disconnect (-) battery's terminal!!!!!! (the SAM anyway is blown)!
Remove plastic clips, and take out boot's rear plastic protector, in order to remove the half left side vertical carpet. Now the SAM is in clear view. Undo the bolt in the top and lying down the SAM in front of it, by turning it, now get it out of its base, and you are ready to unplug connectors. Note which one goes where, and remove it. Also remove from its rails, the anti-theft tow sensor & a vacuum sensor too.
Put all connectors in polybags to keep it clear(ph:299).

Although finally, I replace the chip with professional tools (soldering base and desoldering tool-are expensive), I did exactly the same job with amateur tools & self made desoldering tool (ph:304,5,7,16) , in the second SAM for amateurs (like me in this case). Also there are some other ways to remove & solder the chip. It is in your choice.

a) A 20watt Taivan soldering iron (with two tips, one pinpoint-one hoof.)
b) Thin no-flux solder 1mm
c) Liquid no-flux cleaner(important)
d) Desoldering braid 1,5mm.
e) Alcohol for final clean.(ph:297)

Watch carefully these YouTube videos* and more, do some practice to a useless processor of a dead PC, for desoldering and soldering before attempt to your new already programmed processor.

If you decide to do it by yourself and select the desoldering method as in photos (ha-ha!), you must get a refaced (with a 16mm iron bar), 3/4''to 1/2''bronze plumber's connector, with a 1/2'' tap on it, ( do a 5mm hole on top, to insert - the well welded with instant UHU - wire on top of processor, prior to raise all (ph:310), after heat apply), heated to 450 Celsius, to maintain enough amount of heat, for desoldering 64 pins at once. You must leave it approx.. .5 secs seating square in top of the chip, before starting to raise it (ph:310). The copper one (ph:309), does not work at all, too little thermal amount. Notice, the around the chip solder (ph:308), before the heated bronze insertion (ph:310)), which after melting, equalise thermal amount around the chip and make desoldering, easier and safer .

After chip removed (ph:311), desolder the base pads with desoldering braid(ph:315), make a perfect pin/pad align, and you are ready now to solder the new processor (ph:312,13), following video's soldering tips.

IMPORTANT: Before start desoldering the old and soldering the new, note the marking point for correct reposition, (blue arrow ph:293).
Degauss yourself and go on, .... but........... !

BECAUSE it is very easy to DISTROY the base pads & so everything, is far CHEAPER and BETTER to pay a local PC repair shop, to do the job for you!!!


Visit this site * to order on-line your new already programmed processor, 95€ in front of your door(ph:296,8), mentioning your SAM part no:, and do all above.
This solution is cheaper, than some other, who need to send them the complete SAM for repairing in exchange, and pay for repairing and two p&p.-
After finishing the job (2 hours), put back everything in reverse, weld the cutted plastic piece with melting plast-gun (ph:317), remove keys, and when you are ready to connect the battery's (-) terminal, do it steady with confidence at once, not too fast-not too slow!! (personally I think the SAM's failure occurs during disconnection, not when reconnect the battery). Cross your fingers and start the engine, if you did it the right way, everything will work fine. Mine did!!!

Order on line:

Processor info:


-------- (there are more photos, ask)

B: SOLUTION(the simple one)
If you find a cheap used SAM (around 60-70$), then you can replace it by yourself, and reprogram it, visiting the local MB dealer for 60$, (total cost 120$). Unfortunately the common second hand SAM prices, are about 150-200$,( at least here in Greece). They know exactly what they sale!.

Comments suggestions welcome.


Senior Member
Sep 6, 2008
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Bromley, London
Your Mercedes
CLK 320 CAB Elegance C208
thanks, some good info there although a bit too tech for most I feel.

One of the company's you mention, CodeCard also sell the replacement LCD displays for temp and clocks that so many of us have problems with. Thing is I have never quite mastered soldering these plastic metalised contacts :(


Senior Member
Feb 25, 2009
Reaction score
Your Mercedes
Thats old hat stuff now.
They're working on TRANSPARENT micron layer tracks, printed on using a special printer and solution now (for displays etc.)


New Registration
Feb 25, 2017
Reaction score
Your Mercedes
w204 C200
Hallo I want some help where to ask for w204 rear sam repairing;)

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