E86 Z4 Air Bag warning light - Z4 M Coupe

[djlogan33]

I have had the airbag SRS warning light on for over a year on my Z4 M Coupe.

I have read many posts on different social media websites about the cause of the airbag SRS warning light.
Including: problem with the airbags themselves, a loose wire, a faulty seat belt buckle, or a problem with the Engine Control Unit (ECU)

Very few sites mentioned, many times the airbag SRS warning light comes on after replacing the car battery. I remembered that airbag SRS warning light came around the time I installed a new battery.

I used a C110+ BMW Code Scanner to clear the airbag SRS code and turn off the airbag SRS warning light.

[Clearancediver]

If the light came on after the battery change and came back after clearing…. Check the connector to the BST…. Go look at the positive battery terminal and see the two wire pair that is attached to the BST at the very end. That is the SRS wiring that will “fire” the squib which disconnects the terminal internally to prevent sparking/fire as a result of a crash.

Now trace it back to a connector… probably within 18” of the BST. This connection has a resistance value … 1.2 to 3.4 ohm it must meet. Clean it with electrical cleaner and reconnect… clear codes and see if it eliminates the SRS fault.

Always remember Battery cables need to be disconnected prior to doing this to prevent codes being set.

If you get ISTAD and appropriate cable… you can actually “read” the resistance of that connection if it is faulting.

Don’t trade ease of a portable scanner which is limited in its ability to diagnose for actual BMW diagnostic software which will give/identify repairs …. and the procedures to do so.