SRS fault and light on

[sean d]

Hi Guys, wonder if you can help me with this problem, I replaced my seats with a set of sport seats and got the dreaded light, I have had a b800 on it today and got 2 faults, 11 and 1a, I cleared 11 as that was the passenger seat buckle switch, the code 1a is Seat occupancy detector, passenger: Coding data I have the bypass in place but it still will not clear, my Z3 doesn't have a passenger airbag, does the module need re-coding, thanks in advance
Regards, Sean

[mrscalex]

Usual question although I suspect not as you are getting chassis codes. You are plugged in under the bonnet rather than dash? And you aren't reading the numbers as hex and looking them up as decimal and getting the wrong descriptions?

[sean d]

I'm even more confused now, should I be plugging in to the OBD under the steering wheel, the reading I am getting is table 38 and the code is 1a, I am assuming this is correct as the light only came on when I changed the seats,

[sean d]

Maybe the device displays in both Hex and decimal and thats why I got both codes which are essentially the same 11 and 1A, however I am still getting the code 1A, I am assuming the it is just as 1A rather then 11 as there is a fault code 1A and a fault code 11 in table 38.

[mrscalex]

I'm even more confused now, should I be plugging in to the OBD under the steering wheel, the reading I am getting is table 38 and the code is 1a, I am assuming this is correct as the light only came on when I changed the seats,

Definitely the pacman under the bonnet as only that one can read chassis codes. The under dash is for engine codes only.

[Robert T]

If your car doesn't have a passenger airbag, why do you have an occupancy sensor bypass fitted? You shouldn't need one. Did it come with the seats? This might be what it is complaining about.

Cheers R.

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[sean d]

Hi, thanks for your input but I have tried it with and without the bypass, just to add that my Z is a facelift and the wiring was completely different to the seats so I used OEM harness for both seats.

[mrscalex]

Hi, thanks for your input but I have tried it with and without the bypass, just to add that my Z is a facelift and the wiring was completely different to the seats so I used OEM harness for both seats.

So the car is a facelift but the seat harness wasn't compatible. Does that make the seats pre-facelift? There's no OEM harness to go from pre-facelift seat to facelift car. Only to go from facelift seat to pre-facelift car.

Are you sure you're using a compatible adaptor harness? I had to lash one together when I went from pre-facelift seat to facelift car.

Unless there are 2 types of facelift cabling?

[therealdb1]

You do not say what your build date is but the information I have is that the airbag module changed from MRS II to MRS III at March 1999. Note that is build and not registration date.
As Mr Scalex says the seats may be for the newer module or vice versa and the module that you have is not happy with the signal it is receiving from your bypass.
The circuit diagram shows that the passenger seat occupancy detector feeds directly into an input of the control module and as such it is highly unlikely that you can leave this pin floating. Unfortunately, I do not have information on whether this pin should be high, low, or somewhere in between in the respective states.
Is there any chance you could hook up your car to a BMW specific diagnostic like INPA to try and pinpoint the issue more closely?

[Robert T]

There are plenty of people who have swapped seats in both directions and this is the first time I have seen this issue come up.

What you need to do is to replicate the wiring to that of the passenger seat that was originally fitted to the car. The SRS module seems to be expecting a certain set of inputs that match a car with only one airbag and you have given it something other than this and it quite possibly isn't the same as having the bypass fitted/removed completely. Recoding it won't help as you still don't have a passenger airbag.

I think the codes have to be cleared from the airbag module manually in order to get the light to go out, so if you change anything with the wiring, you need to clear the codes before you test it. And always make the changes with the ignition off, as you don't want any pyrotechnics going off in the car.

Cheers R.

[BladeRunner919]

I agree - I was a little confused about why you had fitted the occupancy bypass to a car that doesn't have a passenger airbag.

[sean d]

So, will the seat need an occupancy sensor connected at all,? If its only for the airbag then it appears not, thanks again for all your input guys its much appreciated.

[gookah]

So, will the seat need an occupancy sensor connected at all,? If its only for the airbag then it appears not, thanks again for all your input guys its much appreciated.

the passenger seat will probably have a seatbelt pretensioner.
the fault could be with that circuit, and as such may still have a seat sensor for this to operate?
I have never known a facelift to not have a passenger airbag either?

[sean d]

Sorted thanks guys, just needed the occupancy pad disconnecting