One of the most common problems that affect Mercedes-Benz vehicles is the failure of SAM modules. 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.
In Mercedes-Benz terms, SAM stands for Signal Acquisition Module.
The most common problem that causes the failure of Mercedes-Benz SAM modules is water damage and corrosion.
What you will need
It is highly recommended to read the codes via Reliable Scanner, which can read SAM errors and re-program SAM or any other modules.
It is important to use a scanner that can pull the codings and backup all the settings in the options.
A cheaper option than buying a brand new module is to buy a used module from another (scrapped) vehicle. If you buy 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, then get apart from a base model, but it's not guaranteed that no programming is needed because some base models have different config.
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 that error codes that are stored are intermittent. Therefore, present codes are current error codes.
- Choose variant codes.
- 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.
- Tilt the hood up to maximum angle.
- 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 flat head precision screwdriver.
- Unplug the ECU connection to the SAM unit.
- Move the wire harness away from the SAM unit.
- 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, be sure that the number of fuses and relays are the same. Also, make sure 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 upper connectors from the main harness. Be sure to secure the main harness.
- Reconnect the 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 coding backup/reserve.
- Choose to restore coding.
- Choose read fault codes again to verify the successful installation and code restoration.
- There should be no more codes related to the SAM module.
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, which means coding is required.