![srs bus srs bus](https://i.ytimg.com/vi/ctFTteKhAf4/maxresdefault.jpg)
As you suggest it is quite a large job to remove the dash and I would need to be 100 per cent that’s where my problem lay before venturing forward. There is restricted access under the dash by the hood release, under the plastic under dash cover, but if you have AC expect this to be a little more crowded. The dash is in 2 halves the upper and lower, just as you say the glove box is moulded into the lower half.
![srs bus srs bus](https://justpostit.in/wp-content/uploads/2020/12/srs-travels-bangalore-Car-Rental-justpostit.jpg)
Grab a torch and have a good look – and smell around and see if you can spot anything. The fuse box under the hood connects through the bulkhead to the wiring loom, there is a chance the wire is damaged in the fuse box (it may have even taken a fuse out in here) Most of the power distribution is done here check the wires to the rear of the connection/distribution fuse and relay board. This resets the SRS lights as before on ignition power, without a star reset. There are 3 wires to connect, colour for colour those that exist under the seat Brown, White and Red on the yellow connector. This seat sensor emulator box, usually around £15 delivered to your door, provides a seat occupied PWM signal output that once connected, fools the ABCM into thinking all is well and that there is a bum on the passenger seat. So strip out the seat and remove the leather etc etc…… OR buy a magic box from China from the large online auction sites.
#Srs bus free#
The RFID token hidden in the child seat is detected by the seat matrix (antenna) and the electronic box then gives out the all important seat unoccupied/child seat in place PWM CAN signal to the ABCM turning off the passenger bags and illuminating the advisory air bag off light.Ī later auto child seat detecting, post face lift, later E Class W210 model, cannot be ‘linked out’ in any way sorry! It needs a CAN keep alive signal to the ABCM to signify that the system is fault free (default seat unoccupied signal) so any fault occurring in the wiring or seat matrix resulting in the PWM output failing will deny the function of the passenger airbag by default and raise the SRS dash lamp along with the orange air bag transmission mounted indicator. The other function of the electronic box within the seat is to auto-detect the presence of the MB child seat, this is done by using RFID (radio frequency identification) working in the same way as the detection alarms at the doors of music shops etc. Once the seat is sat on, the electronic box in the seat changes the frequency of the pulse which is again detected by the ABCM to turn the passenger bags on.
![srs bus srs bus](https://content3.jdmagicbox.com/comp/haveri/i1/9999p8375.8375.191112200117.r7i1/catalogue/srs-travels-haveri-x2oawpukup.jpg)
This beat is detected by the ABCM (Air bag control module) when the seat is unoccupied and turns off the air bags on passenger side. There is an electronic box inside the seat base that forms part of the sensor matrix, the ends of the wire ‘maze’ are connected to this and it converts the status of the occupancy detector into a CAN output signal that is piped to the Air Bag Control Module (as a PWM signal) An over simplistic way to imagine this, is to think of it as a pulse, like a heart beat at a fixed rate.
![srs bus srs bus](https://www.srstravels.net/images/servicesimage1.jpg)
Post face lift set up is far more complex. On cars pre face lift, without auto child seat detection, the connection from the seat occupancy sensor is connected directly to the Air Bag Control Module and operates just as a simple switch, changing the potential of the signal line to the module when sat on.