12 42 540 Replacing Safety Battery Terminal (SBK)

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2013 BMW 128i, 2012 BMW 128i, 2011 BMW 128i, 2010 BMW 128i, and 2009 BMW 128i. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION:

Observe safety regulations .

Investigate cause of triggering of safety battery terminal.

To do so, read out fault memory of airbag control unit. Note fault messages stored in memory. Rectify faults. Then clear fault memory.

Use of safety battery terminal:

From model year 1998 in Series E38, E39, E46
From 4/99 in E36/Z3
in each of following new Series

The different models have different installation locations:

Battery in engine compartment

Safety battery terminal is replaced with cable up to battery positive support point.

Safety battery terminal is omitted as from 03/2002 from all E46 LHD models with 4-cylinder engines.

Battery in luggage compartment behind side trim panel

Remove side trim panel.

Follow instructions for disconnecting and connecting battery. See 12 00... Instructions For Disconnecting And Connecting Battery .

Disconnect and cover battery negative lead. See 61 20 900 DISCONNECTING AND CONNECTING BATTERY NEGATIVE LEAD (CONVERTIBLE) or 61 20 900 DISCONNECTING AND CONNECTING BATTERY NEGATIVE LEAD (COUPE) .

Fig 1: Removing Side Trim Panel

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Release front side trim panel partly and fold forward.

Fig 2: Releasing Front Side Trim Panel

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Battery in luggage compartment under floor trim panel

Follow instructions for disconnecting and connecting battery.

Fold back floor trim panel (1).

Lift cover (2) on battery negative lead.

Disconnect and cover battery negative lead (3).

Release nuts (4).

Remove battery cover.

Fig 3: Identifying Back Floor Trim Panel & Cover Battery Negative Lead

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Battery in luggage compartment under spare wheel

Remove spare wheel.

Release screws.

CAUTION: Do not kink air pipes.

Set air supply system (1) to one side.

Follow instructions for disconnecting and connecting battery.

Disconnect battery negative lead. See 61 20 900 DISCONNECTING AND CONNECTING BATTERY NEGATIVE LEAD (CONVERTIBLE) or 61 20 900 DISCONNECTING AND CONNECTING BATTERY NEGATIVE LEAD (COUPE) .

Fig 4: Locating Air Supply System Screws

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Disconnect supply cable (1) for vehicle electrical system.

Installation:

Remove faulty fuses and carry out troubleshooting.

Fig 5: Identifying Supply Cable For Vehicle Electrical System

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CAUTION:

Pay attention to interface.

The repair cable is always a standard length.

The heavy-current connector of the repair cable has a larger diameter than the battery positive lead.

In some Series (e.g. E46 touring), the heavy-current connector of the repair cable can lead to installation problems.

This is the case when the interface is in the area of the close-fitting trim panels.

Find matching interface (e.g. approx. 10 cm behind rear seat backrest in E46 touring).

Lay repair cable parallel to battery positive lead.

Mark interface of battery positive lead at end of repair cable.

Fig 6: Identifying Mark On Battery Positive Lead At End Of Repair Cable

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Release cable ties (1).

Disconnect plug connection (2).

Fig 7: Identifying Cable Ties & Plug Connection

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CAUTION:

Do not use bolt cutters or similar tools to cut through the cable.

A cable end that has been squashed flat will no longer fit into the clamping sleeve.

Saw through battery positive cable at marked point with an iron saw.

Fig 8: Locating Cable End & Clamp

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Strip insulation - length (A) - from cable end.

Distance (A) = 15 mm.

Fig 9: Identifying Strip Insulation Length (A) From Cable End

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Push heavy-current connector (1) over stripped cable end and screw into position.

Fig 10: Identifying Heavy-Current Connector

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Push shrink-fit hose (3) over repair cable.

Screw threaded sleeve (1) of repair cable (2) to heavy-current connector.

Fig 11: Identifying Shrink-Fit Hose & Threaded Sleeve Of Repair Cable

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Push shrink-fit hose (1) over connecting point and shrink on with a hot-air blower (2).

Fig 12: Pushing Shrink-Fit Hose

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NOTE: Heat up shrink-fit hose until it has settled completely around the connection point.

Fig 13: Locating Shrink-Fit Hose

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When laying the repaired battery positive cable, observe the following:

The shrink-fit hose must not be scuffed during any movement.
The repair cable must not cause any disturbing noises during driving operation.

NOTE:

Offsetting cutting line by approx. 10 cm produces excess length of battery positive lead (1).

Lay battery positive lead (1) without kinks or abrasions. (Shown on E46 touring.)

Fig 14: Identifying Battery Positive Lead

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