Navigation-Computer Supply Signals

'Professional' Navigation System

The navigation system works out the route and provides the directions to a defined destination.

GPS Navigation (Global Positioning System): The GPS navigation system pinpoints locations by means of the signals transmitted by satellites. The signals are received by the GPS antenna on the vehicle, processed by the GPS receiver and passed to the navigation computer as latitude and longitude data. From that information, the navigation computer calculates the vehicle's location to within 100 m.

Correct operation of the GPS navigation system is only possible when there is an unbroken line of sight between the GPS antenna and at least two GPS satellites. In underground car parks, tunnels, etc. GPS function will be impaired or impossible.

Brief description of components

GPS antenna
The GPS antenna receives the signals from the satellites. The signals are passed to the navigation computer. The GPS antenna is mounted on the roof at the rear.

Navigation computer with integral GPS receiver, CD-ROM drive and gyroscope.
The navigation computer is located in the trunk on the left-hand side under a flap and is cooled by an integral fan. If it is not being adequately cooled, it is shut down due to excess temperature and a message displayed on the control display.

Integrated in the navigation computer are a GPS receiver and a CD-ROM drive as well as a gyroscope.

The gyroscope (inertia sensor) detects the force that occurs when there is a change of direction, e.g. when making a turn. The voltage signal resulting from the force detected is fed to the navigation computer.

The navigation computer is a node in the MOST network.

Roadmap CD
The roadmap CD contains all the information the navigation computer needs to be able to plan routes. The roadmap CD must be handled with care. Scratches on the CD may cause system crashes or loss of function. If such a symptom is present, carry out function tests with a new/undamaged CD. A CD which functions in a navigation computer without giving rise to complaint is not necessarily free from faults.

Wheel-speed sensor
The wheel-speed sensor sends signals to the navigation computer from which it calculates the distance traveled. The standstill pulse is also displayed in the diagnostic request. The pulses can fluctuate between 0 and 1 at a standstill. The number of pulses increases with the wheel speed.

Control display (CD) and controller
The control display shows the navigation system displays and control options. Operation is by means of the controller located on the front of the center armrest.

Instrument cluster
The instrument cluster can also display navigation system information in conjunction with the control display.

Audio system controller (ASK)
The audio system controller (ASK) is a control module in the MOST network. The ASK manages all audio signals.

MOST (Media Oriented Systems Transport)
The MOST bus is used for the transmission of audio (sound), video and navigation system signals.

RGB lines for video signals
The RGB lines (red/green/blue lines) are used to transmit video signals to the control display.

Main functions

Location calculation
The navigation computer calculates the vehicle's location by analyzing data from
- the wheel-speed sensor
- the gyroscope and
- the GPS receiver

Location calculation by Match function
The Match function continually compares the current vehicle location with its expected position along the route. Discrepancies identified are corrected.

Learning function after a tire change
After a tire change, the navigation system automatically learns the correction factor for the tire size while the vehicle is being driven. There may be incorrect location calculation during the correction. The learning procedure is completed after a few miles.

Route planning
The navigation computer calculates the required route from
- location data and
- data from the roadmap CD.

In order that the routes displayed match the actual road system, the roadmap CD used must be up-to-date with the latest information.

To work out a route enter/select the following on the control display using the controller:
- the destination details
- the selection criteria for the desired route (fastest, shortest, etc.)

NOTE: large discrepancies between the information displayed and the actual road system are an indication of GPS reception problems.

Operation
The navigation system can only be selected using the controller when the roadmap CD is inserted in the drive.

Displays
There are two ways in which the navigation system information can be displayed on the control display:
- arrow display or
- 2D map display.

Audible warnings of approaching turnoffs are issued (via the audio system controller).

NOTE: If the driver does not follow the route instructions an alternative route is automatically calculated and displayed.

The tachometer on the instrument cluster can also display the following information in conjunction with the control display:
- the guidance indicator (round arrow),
- the next intersection and
- the distance to the next intersection.

Until shortly before the next turnoff, the distance to it is shown in figures. It is then shown in the form of a bar indicator. The bar shrinks continuously as the turnoff approaches.

Whether the distance to the next turnoff is shown in figures or graphically is decided by the navigation system.

Service functions

Loading the operating software
A new version of the operating software is installed as follows (observe instructions on CD):
- Turn on terminal R and wait until navigation system is ready for operation.

NOTE: make sure the electrical system voltage is stable. There must be no change of terminal status while the software is being loaded.

- Remove roadmap CD from navigation computer.
- Insert software CD in navigation computer.
A percentage display appears after a few seconds in the control display. The percentage display shows the progress as the software is being loaded.

When loading has been completed, the following message appears: "The software has been successfully loaded."

- When the software has been successfully loaded, remove the software CD.
- Confirm completion of the process by pressing the controller.

Coding of navigation computer
NOTE: load the operating software first!
After loading the operating software, encode the navigation computer.

Initializing on vehicles with BMW ASSIST
Initialization may be necessary on vehicles with BMW Assist.

Replacing the navigation computer on vehicles with BMW ASSIST
After replacing the navigation computer, a road test of about 15 minutes is necessary. GPS reception and GSM reception must be guaranteed. (Global Standard for Mobile Communication, the mobile communication network)

Problems with navigation
Location calculation is performed among others with the GPS receiver. It is vital that the navigation control module is supplied with power. The power supply is checked by selecting navigation. Observe Help for MOST network. The unit has GPS reception when the globe in the control display is shown on a green background. In order to have GPS reception, the vehicle must be located in large outdoor area. The antenna must be checked if there is no reception. A voltage supply of 9 - 14 V and the diagnostic requests are important to the antenna.

The control module software must be checked if the MOST network is functioning but navigation cannot be selected.