E31 Flashing Srs (Airbag) Light Repair

Problem – SRS light on dashboard continually flashes.  Did so since the day I bought the car!

Diagnosis – CarSoft reported error with front left sensor.  Clearing error via carsoft made no difference.

There are but two sensors, plus the airbag module itself, for 1993 model year.  The plastic was very brittle and the connector disintegrated straight away!  (Orange part in picture – airbag parts and connectors are always orange on this car and most BMWs I think for easy identification).

Attempt 1 – substitute sensors from my 1989 750iL which I very stupidly removed without disconnecting the battery first so now the SRS light is flashing there and carsoft won’t talk to the 1989 module… Sigh.  Carsoft on the 850Ci gives the same error as before.

Attempt 2 – swap the left sensor onto the right and vice versa – should have done this instead of step 1!  Carsoft still gives same error.

Therefore suspect the wiring is at fault or the module itself…  Module errors seem very very rare as I couldn’t find any other forum posts about them.  The module is located under the passenger side glove box which needs removed and even then access is very awkward it’s recessed up and hidden by another module (or two depending on options).  The wiring looks ok – and to test it end to end I’d have to access the module anyway, so time to take a chance on a new module…

You can buy them for $900 new, or Ebay from between $20 and $80 depending on whether you have single or double airbag version.  Check the part number!  Of course I went for the Ebay one.

The official E31 service manual gives good instructions for removing the glovebox and associated pieces.

And the usual advice - disconnect your battery (or batteries for most E31′s) before working on any airbag parts!

So new module plumbed in – reconnect batteries – turn on ignition – flashing light still there

However, after a period of annoyance I checked with Carsoft and different error codes were present – clearly ones from the donor car which had probably been powered up with disconnected sensors and logged the fault.  Cleared those codes, and flashing light gone – everything working fine now!