Mercedes-Benz vehicles including E, C, S, CLS, ML, GL, R, G Class, may display the following warning messages on the instrument cluster.
- Front Passenger Airbag Disabled See Oper. Manual
- Front Passenger Airbag Enabled See Oper. Manual
To temporarily remove the warning message, press the reset button on the steering wheel or instrument cluster. In many cases, the error message comes back again when the passenger seat is occupied/vacated or when the vehicle is restarted.
Other possible symptoms related to this problem include:
- Airbag light on but NO airbag codes present
- There will be no fault codes in the airbag module. If you check the EVENT MEMORY of the airbag module or the WSS module, you find an error message stating WSS not calibrated.
- Front Right SRS Malfunction Service Required
- Restraint Malfunction error on the instrument cluster
- 9A04 Component WSS is incorrectly adjusted
This message may also come up if there is a Mercedes-Benz child seat on the front passenger side. If you have an adult or don't have any passengers present but are getting any of these messages, it means a malfunction has been detected by the Weight Sensing System , also known as WSS or N2/13 control module. The main input for the WSS module is the four weight sensing sensors located in the passenger seats known as B48/11, B48/12, B48/13 and B48/14.
Passenger seat weight sensor detects the weight of the person on that seat. This is important because if the WSS detects low weight, in other words, a child on the passenger seat, it will not deploy the passenger airbags because they can cause injury to the child.
Troubleshooting Step 1
To fix this problem, the first thing that you need to do is check if there are any objects below the passenger seat that may be obstructing the movement of the seat. Move the passenger seat all the way FORWARD and UP and check for objects including in the seat tracks.
Once you remove any objects below the passenger seat, cycle the ignition on and wait for at least 1 minute. No passenger should be seated on the passenger seat.
Turn off the ignition and turn it back on. Hopefully, the error message is gone. If the error message remains, move to the next step.
Next, Perform Mercedes WSS Initial startup/recalibration
If the problem remains the next step is to perform WSS (Weight Sensing Sensor) calibration. To calibrate Mercedes weight sensor module, you will need the official Star Diagnostic Scanner used by the dealer or a Professional Diagnostic Scanner used by auto mechanics. You can NOT perform WSS calibration with scanners such as iCarsoft MB II or Launch Creader.
Various weights were used to simulate a child and an adult sitting on the passenger seat. First, you calibrate the seat with no weights on. Next, you calibrate the passenger weight sensors with 17 kg and 44 kg.
A bag of the concrete mix was used to simulate the 44kg weight.
The WSS calibration may vary slightly depending on the scanner. Here are the general steps and some important tips to keep in mind when calibrating the passenger weight sensor on Mercedes-Benz cars.
- When asked to move the seat FORWARD and UP. Do so but once the seat gets all the way to the front, bring it back 3 to 4 inches and down about one inch. This will set the ZERO POINT SETTING.
- At first, you will calibrate the seat with no weights on. Once that step is completed you will be asked to calibrate the seat with 17 kg of weight on the seat. There is a special tool for this, but you can complete this step using any object that weights 17 kg (+/-1). You want to make sure the weight is evenly distributed on the passenger seat and no concentrated in one spot.
- Lastly, you will calibrate the seat with 44 kg. You can add an addition 27 kg or remove the previous 17 kg and add the full 44kg.
- Position the backrest in the vertical position.
- Keep the headrest in the lowest position at all times.
How to calibrate seat weight sensor module
Below you will find general instruction on how to perform Mercedes WSS Calibration.
- Connect your scanner to the OBD-II port under the dashboard.
- Once the scanner is powered up, go to the WSS module
- Select WSS Calibration, Initial Initiation or Recalibration depending on the scanner.
- In the next step, you will have to move the seat FORWARD and UP to register this as the zero position. Then you move the seat towards the middle, then back, then down.
- Repeat the steps in 4 with 17 kg weight on the passenger seat.
- Repeat the WSS calibration steps 4 again with 44kg on the passenger seat. (Add 27kg in addition to the 17kg or simply remove the 17kg weight and add the full 44kg.)
Here is another example on how to perform Mercedes passenger weight sensor calibration using Autoland ISCAN II professional scanner.
During passenger weight sensor calibration you may get the following errors.
9A02 Zero point setting not Completed
- When asked to move the seat all the way FORWARD and TOP, do so then move the seat back 3 inches and down 1.
- Make sure you are moving the seat as asked during each step.
That's it. In summary. First, remove any objects from under or behind the passenger seat first. Hopefully, that will reset the error message. If not, Mercedes passenger weight sensor may go out of sync and will need recalibration. Take your car to a mechanic (who specializes in Mercedes cars) or the dealer to perform passenger weight sensor calibration. The average cost for this procedure ranges from $150 to $250. The calibration procedure takes approximately 30 minutes and any mechanic with the right scanner should be able to perform this procedure.