Updated on Reading Time: 6 minutes
In this article, we go over the steps on how to troubleshoot a SAM module, replace a Front SAM module on a W203 C-Class and code the replacement SAM unit. The most common problem that causes the failure of Mercedes-Benz SAM modules is water damage and corrosion.
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In Mercedes-Benz terms, SAM stands for Signal Acquisition Module. One of the most common problems that affect Mercedes-Benz vehicles is the failure of SAM modules.
What you will need
Tools:
YOUCANIC Pro Manuals
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- Torx screwdriver
- Flathead precision screwdriver
Parts:
- New or Used Mercedes SAM unit.
Reading the codes from the SAM module is the first step, but you will need a Reliable Scanner, like the YOUCANIC Full System Scanner, which can read SAM errors and clear the codes after you replace the module. To avoid having to program the replaced SAM, find a used replacement SAM with the same part number as your old SAM.
It is important to use a scanner to read the SAM codes and clear them after you replace the module.
A cheaper option than buying a brand-new module is to buy a used module from another (scrapped) vehicle. If you believe a unit from another vehicle, be sure to match the part no, so it is unnecessary to re-program the module.
If your car is a base model, get apart from a base model, but it’s not guaranteed that no programming is needed because some base models have different configs.
How to diagnose Mercedes SAM
- Choose a model from the scanner menu.
- Choose Control Units, then SAM acquisition module front.
- Read fault codes.
- Below are samples of fault codes with descriptions.
- Please note thaterror codes that are stored are intermittent. Therefore, present codes are current error codes.
- Choose variant codes.
- Backup-variant-coding
- Write a filename for backup. Backing up will store every setting from the target vehicle.
- The front sam module also controls Auxillary Water Pump (windshield washer), Cornering Lamp (fog light illumination on the selected turn at low speed), etc.
Replacement
- Tilt the hood up to the maximum open position.
- Disconnect the negative terminal of the battery.
- Separate the wiper arm connector using a flat screwdriver.
- Move wiper arms aside to provide more room for the removal of the SAM module.
- Please take pictures of the connectors or label them in case you forgot the matches.
- Disconnect connectors using a flathead precision screwdriver.
- Unplug the ECU connection to the SAM unit.
- Move the wire harness away from the SAMunit.
- Remove retaining screws using a Torx screwdriver.
- Remove the fuse, which would prevent the SAM from coming out.
- Move the wiper arm towards the front of the car to make room to remove the SAM.
- Pull the SAM gently to expose the connector under it.
- Retake pictures or mark the connectors before removal.
- Disconnect bottom connectors.
- Compare the replacement SAM with the old SAM, ensure the numberof fuses and relays are the same. Also, ensure that all the fuses and relays have the same amperage rating.
- Reconnect bottom connectors. You may use the old SAM to help with the connector pattern. Also, make sure that no connectors are left behind.
- Lower the SAM module to its original position.
- Reconnect the fuse.
- Reinstall retaining screws.
- Reconnect upper connectors, including ECU connectors.
- Reconnect the upper connectors from the main harness. Be sure to secure the main harness.
- Reconnectthe wiper arm.
- Install SAM cover make sure it seals in place properly to avoid water contamination.
- Reconnect the battery.
- Read Fault using a scanner to determine if there is a problem with the replacement SAM.
- Clear fault codes.
- Choose clear codes. There should be no more codes related to the SAM module.
If you purchase a brand new SAM from the dealer, it MUST be coded and programmed. If you purchase a used SAM that has matching part numbers, in most cases, all you need to do is install the SAM and clear the codes. In some very few cases, you may need to perform programming of a used SAM if the options of the donor SAM don’t match that of your vehicle.
Does a SAM unit need to be programmed on a Mercedes-Benz?
- Yes, a Mercedes-Benz needs to be programmed.
Can you install a used Mercedes-Benz SAM unit?
- Sometimes. On the Mercedes-Benz model made around 2000, it was easier to swap used SAM modules. You can install a used SAM, but we strongly recommend that the used unit be programmed.
Will the engine start if I install a used Mercedes-Benz SAM unit?
In most cases, the vehicle will start with a used SAM. If you install a used SAM, the engine may start, but several features may not work, so coding is required.
Part Number
- 2035454701
We hope you find the Mercedes-Benz SAM Module Replacement Guide helpful. Check these troubleshooting and repair guides for more help on your Mercedes-Benz.
Written and fact-checked by:
YOUCANIC Techs YOUCANIC articles are written by authors who collectively have over 60 years of experience in the automotive field and years of hands-on experience on vehicles. These authors are certified ASE G1 Automotive Maintenance engine professionals (the highest level certification for vehicle maintenance and repair). They hold associate’s and bachelor’s degrees, as well as having gone on to further study to receive a master’s and doctorate degrees. These authors collaborate on research, writing, editing, and fact-checking every article to ensure that it is accurate and up to date and delivers the best counsel and information to YOUCANIC readers. View all postsRush*t Hila is an engineer and ASE certified in G1 Automotive Maintenance 
