2003 z4 3.0i bst

[Iain2152]

Hello there this is my first post.i bought a 2003 z4 last year it runs and drives great but bought as a project as needing painting and a few electrical faults.alread had power steering pack up after driving 60 miles sorted that by sending motor away for repair.just now I'm preparing body for paint and having a look at airbag system.car had a failure for srs light on but now no srs light on at all so presume has been disconnected or bulb removed,still to investigate this.i do have some fault codes and have noticed in the boot the 2 wires going to the bst have been cut and there is a single wire coming from the positive terminal needing to know what this wire feeds as I'm not getting any voltage on it I know you can fit a resistor to the cot wires to remove code but need to know purpose of the single wire don't seem to be able to find a wiring diagram any help would be good before I start ripping car apart thanks. Iain

[Street]

Welcome to the forum. This might help you:

Battery terminal isolation
The battery cable is fitted with an electrically conducting shield, which is insulated against the body and against the battery cable. The shield consists of a low-impedance metal mesh. A cable exits from each end of the shield, i.e. at the safety battery terminal in the luggage compartment and at the battery earth point in the engine compartment. The adapter cable at the safety battery terminal is connected to the right B-pillar satellite, the adapter cable in the engine compartment to the left B-pillar satellite. In order to minimise the danger of fire in the case of damage to the cable, the battery cable is monitored by the following satellites:
Satellite, B-pillar left
Satellite, B-pillar right

Brief description of components
Safety battery terminal
The battery safety terminal is installed in the positive lead (charge wire) from the alternator just in front of the positive terminal of the battery: The cable ends in a tapered plug. If the monitoring of the battery cable determines a short circuit, the safety battery terminal is triggered by the right B-pillar satellite. This switches off the alternator and the fuel pump.

It also deactivates the starter motor load circuit. The engine can no longer be started.

The interrupted alternator line can be replugged provisionally to restart the engine. In this case, however, the battery terminal isolation function is no longer available as the priming cap has already been ignited. The priming cap and alternator line must then be replaced.
The battery cable is fitted with an electrically conducting shield, which is insulated against the body and against the battery cable. The shield consists of a low-impedance metal mesh. A cable exits from each end of the shield, i.e. at the safety battery terminal in the luggage compartment and at the battery earth point in the engine compartment. The adapter cable at the safety battery terminal is connected to the right B-pillar satellite, the adapter cable in the engine compartment to the left B-pillar satellite. In order to minimise the danger of fire in the case of damage to the cable, the battery cable is monitored by the following satellites:
Satellite, B-pillar left
Satellite, B-pillar right
Brief description of components
Safety battery terminal
The battery safety terminal is installed in the positive lead (charge wire) from the alternator just in front of the positive terminal of the battery: The cable ends in a tapered plug. If the monitoring of the battery cable determines a short circuit, the safety battery terminal is triggered by the right B-pillar satellite. This switches off the alternator and the fuel pump.

It also deactivates the starter motor load circuit. The engine can no longer be started.

The interrupted alternator line can be replugged provisionally to restart the engine. In this case, however, the battery terminal isolation function is no longer available as the priming cap has already been ignited. The priming cap and alternator line must then be replaced.

[paddy wright]

Good to see you saving an unloved zed- share some pics when you get time

[Iain2152]

Ah problem solved it a shield thank you for the information also got some pics

[Mr Tidy]

Hi and welcome to the forum Iain.

It's always good to see an unloved car getting some TLC.

Iain.