Power steering — device (BMW 3 Series E46)

Steering column components and steering wheel

The rotation of the steering wheel is transmitted by the driver through the steering column and steering gear, as well as the steering rods to the wheels of the car. The steering column can be adjusted manually in height and in the longitudinal direction.

The effort required to turn the wheels, especially when the vehicle is stationary, is reduced by the presence of a power steering system. The power steering system consists of an oil pump, an oil reservoir, and oil lines. The oil pump is driven by the engine through a ribbed V-belt. The pump sucks oil from the reservoir and delivers it to the valve body under high pressure. The valve body is located in the steering mechanism. It is mechanically connected to the steering column and, depending on the direction in which the steering wheel is turned, directs the oil to the corresponding side of the working cylinder. Here, the oil acts on the piston with the toothed rack, thus reducing the effort required to turn the steering wheel.



The steering wheel contains an airbag. The airbag is a folded bag that inflates with air during a frontal collision, thus protecting the driver's torso and head from impact with the steering wheel. During a frontal collision of a certain force, a small charge is ignited in the airbag via the control unit. The explosion produces gases that fill the airbag within a few milliseconds. This time is enough to cushion the driver's torso as it rushes forward. The airbag then folds back within a few seconds, as the gases escape from the bag through the exhaust ports.

Welding and straightening work on steering components is not permitted. Self-locking nuts must be replaced with new ones.

Safety precautions when handling an airbag

Next to the driver's airbag in the steering wheel, there is a front passenger airbag above the glove compartment, side airbags in the doors and a head airbag above the doors. It is not permitted to install a child seat or any other device for restraining children in a direction opposite to the direction of travel in the front passenger seat. In addition, there must be a sign on the door pillar, sun visor or on the instrument panel on the right side stating "no child seat in front". Failure to do so may result in a fine from the German police.

When removing and installing the airbag unit, the following must be observed:

1. Disconnect the negative (-) battery cable with the ignition off. The battery is located in the luggage compartment behind the cover on the right side. In BMW 316i, 318i cars, the battery is located in the engine compartment.

Disconnecting the battery will erase the fault memory of some control units. If necessary, read the fault memory before disconnecting the battery. Refer to Section Troubleshooting. It is advisable to carry out the work in a service station.

2. Insulate the negative (-) terminal of the battery to prevent accidental contact.

3. Before installing the airbag, check again whether the negative battery cable is disconnected.

Failure to follow these instructions may result in failure of the airbag system.

General safety precautions

After removing the airbag, store it with the soft side facing up.

When connecting the battery, no strangers are allowed in the vehicle.

If there is a break in work, the airbag must not be left unattended.

It is not allowed to disassemble the airbag unit. If there is a fault, it will be replaced as a whole. Since the airbag contains explosive material, it must be stored securely. The airbag must be disposed of by a BMW service station. Under no circumstances should you dispose of the airbag yourself. There is a risk of explosion!

A steering wheel containing an airbag may only be replaced with a steering wheel approved by the vehicle manufacturer.

The soft side of the airbag should not be covered, wrapped or treated in any way. It should only be cleaned with a dry or damp towel and a cleaner approved for use by the manufacturer.

If the airbag has been deployed as a result of an accident, the airbag control unit, airbag unit and contact unit must be replaced.

The airbag unit and control unit are sensitive to impacts. If they have fallen from a height of more than 50 cm, they must not be used any more. If the airbag has fallen from a lower height, it must be checked at a service station.



The airbag may only be checked at a service station. Under no circumstances should a test lamp, voltmeter or ohmmeter be used to check the airbag.

When welding, the welding machine terminal must be located in close proximity to the welding site. It is imperative to isolate the negative battery cable and the battery pole to prevent accidental contact. It is necessary to disconnect the plug connections of the airbag to the gas generators.

The airbag unit and control unit must not be exposed to temperatures above +75°C, even for short periods.

Observe the instructions regarding the seat belt tensioner, refer to Section Seat Belt Tensioner. Basic Information and Safety Precautions.

Safety instructions for driving

An airbag does not replace a seat belt. Passengers in a car must wear seat belts to ensure optimum safety.

No child restraint devices are permitted on the driver's seat. Children under 12 years of age may only be seated in the rear seat.

No objects must be placed between the airbag and the person.