[Clearancediver]

Here’s the thing… if you didn’t disconnect the battery prior to disconnecting any connection/connector…. You can and will cause a fault. Anytime you cause a fault it will in almost all cases show up on your dash as a fault light and those that don’t are stored in memory. Lots of posts on this by the way.

You need to clear the faults with software … most BMW specific code faults can’t be cleared using handheld scanners… unless they are the very expensive ones. It is always better to download INPA (old BMW tech software) or the newer version ISTA(D)… commonly referred to as ISTAD. ISTAD has the TIS (technical instructions and diagnosis and repair instructions) built into it. You need a USB to ODBII (OBD2) cable (switchable as pre and post Z4’s have a cable pair switched post facelift) to connect an old computer to your car. You can get the software via download and the cable via Amazon/eBay purchase. There are lost of YouTube tutorials on how to use.

Everytime…and I do mean everytime you disconnect a connection on the SRS system it will show up as an Airbag fault… which “must” be cleared using software…..again very few handheld’s are capable of reading BMW specific codes and those that do don’t have the TIS capablity to dig into a fault and diagnosis the issue and provide repair suggestions. Oh… the connections under the driver/passenger seats have SRS wiring running through those connectors.

As an example… I have a ‘04 …. Battery is in a “hole” under the trunk liner. There is a two wire pair that goes to the BST (look it up if unfamiliar)… I disturbed it when changing the battery (Issue diagnosed prior via BMW technician when happened upon purchase). Got the airbag fault…. Using ISTAD it showed that the resistance to the SRS system was once again (recurring issue for me) more than 3.4 ohms resistance. This time cleaning etc didn’t work and I had to cut out and replace the connector to get the resistance between the mandated 1.2-3.4 ohms required. The fault was specific enough reading in ISTAD to isolate it to that circuit/connection and gave me the ability to read the resistance via ISTAD. Hand held scanner showes it as a being an issue with seatbelt tensioner.

So…. Download ISTAD… buy the cable and educate yourself on how to use via YouTube tutorials….. you will save yourself a lot of heartache in your rebuilt.

Oh…. Always read and note the codes…. Clear and then turn the ignition on and read it again….. what remains is what you are interested in chasing down and fixing….

Have fun……