Build Seat Occupancy Bypass - Airbag light fix

If you find are having a problem where your BMW is showing an "airbag" or "restraint System failure" warning light for no apparent reason, it can more often than not be due to a faulty occupancy sensor in the passenger seat.
This sensors job is to tell the car that there is a passenger sitting in the seat so in the event of an accident, the car knows to fire the passenger airbag. The mat sensor is a very common problem in many BMW models and can be damaged from something as simple as kneeling on the passenger seat. You can have the seat sensor replaced entirely by a dealer but this requires the seat to be removed from the car, stripped of its upholstery and can cost as much as €600 as it takes a few hours to complete.
This little mod is a very simple one that mimics the values sent back to the car by the original seat sensor when in good working order, so the car will always assume there is a passenger sitting there and will fire that airbag if the situation arises. If the warning you are having is intermittent then you most likely wont have to visit a dealer to have it reset afterwards. If the airbag warning is always on then you will have to have it reset afterwards. You shouldnt need to spend any more than a couple of euro for the parts to do this mod, My own cost 4-5 quid and i have enough to do about 50 bypass rigs.

Hope you find this useful and feel free to have a look through my channel for more useful/funny/weird video's. :)

Category:

Howto & Style

Tags:

• airbag
• light
• srs
• restraint
• system
• failure
• seat
• occupancy
• sensor
• bmw
• beemer
• series
• 1er
• 3er
• 5er
• 6er
• 8er
• germany
• german
• car
• sedan
• idrive
• obdii
• obd
• bod2
• canbus
• diagnostics
• eml
• engine

[MyDegis]

Have you done any testings before posting this video? do you know that by using this configuration you only disabling the airbag light. The canbus under the seat has AC/DC 4V that is shifting in the occupancy mat all the time and if you check with the scanner you will see that occupancy mat is still faulty... which is not what it supposed to be. (i'm electronics engineer) . You need the right load and phase shift to fool the computer.

[tiganhonda]

@MyDegis The system runs a check for errors every time you start the car and if there is a problem found, the ECU will instruct the ACM to disable, preventing the bags from firing. With this resistor in place, the ACM never gets the signal that there is a fault with the mat, instead it gets the signal that the seat is occupied and functional. You can scan the car with anything from Carsoft, GT1, INPA etc and you will clearly see there is no fault reported.

[MrAtanasDimitrov]

Hello mate. I have a question about the "bypass" with this type of sheme you use it only tells to the ECU that the sensor is OK. but there is no one on the seat. One my friend told me another sheme with Resistor 56 kOhm, 5%, + capacitor 100pF, 500V + 1/4w + Diode 1N4002, 1A, 100V that give's more resistance and tell to the ECU that there is somebody on the seat. Is it right???

[tiganhonda]

@MrAtanasDimitrov Hi, Im not quite understanding what you mean. This device will give the signal that there is a passenger present in the car, if thats what you are asking.:)

[tiganhonda]

@MrAtanasDimitrov Im still not very sure what you mean but sometimes you dont need software to reset the light, it depends on your circumstances, and yes, this will tell the ecu that there is a person in the seat.

[MrAtanasDimitrov]

I wonder whether it is true, because I did the same model as yours with two resistors and one diode and the light went out on the dashboard without having to remove software. A way that I suggest you should remove the software or it will not extinguish the lamp.

[MrAtanasDimitrov]

@tiganhonda What I mean is that the resistors and diodes that you use in the clip simply telling the ECU that the sensor is OK, not that there is someone sitting on the seat. A variant which I tell you with a resistor and capacitor diode gives more resistance and reported that there is someone sitting on the seat of such data gives the ECU. Is it right that ??

[tiganhonda]

@MyDegis That's incorrect, If you read back on the comments you'll see I described how it operates when installed.

The resistance at this resistor is equal to that of a perfectly functional seat that is being sat in. That means that in the event of an accident, regardless of whether there's a passenger in the seat, the passenger airbags (dash and door) will fire if the accident is severe enough.