System Components

System Components

Mk-3 Navigation Computer




The Mk-3 navigation computer is located in the left side of the vehicles trunk or cargo area. (In the case of the Z8 it is installed in the storage box behind the passenger seat.)

The navigation computer housing contains:
- Map CD drive
- Hardware for navigation function
- GPS receiver
- Gyro sensor
- Output for audio interface
- Output for visual display
- Cooling fan for unit

There are two different hardware versions available dependent on the angle of installation in the vehicle (horizontal or vertical). The Mk-3 is compatible with both board monitor or MIR display units.






Identification of the Mk-3 computer over the previous versions is easy due to a change in the face plate design and the elimination of the "CD-IN" LED.




GPS (Global Positioning System) Receiver
The GPS receiver module of the previous Mk-2 system is integrated into the housing of the Mk-3 computer, further reducing the complexity and the number of components used in the system. The receiver is not serviceable.

The GPS receiver is responsible for receiving the satellite signals and providing the vehicle's position information to the navigation computer.

Information provided by the GPS receiver to the navigation computer can be displayed in the service mode (see workshop hints) but is not typically used in diagnosis.

Gyro (Rotation) Sensor
The navigation computer contains the electronic (piezo) Gyro sensor that detects rotation (yaw) of the vehicle as a confirmation that the vehicle is turning. The signal provided by the gyro is a mili-voltage that changes as the vehicle rotates. The navigation computer uses the input to track the vehicle along the digitized map and display the exact vehicle position.

The signal is available in the sensor test page of the service mode for diagnosis. The sensor is not a separately serviceable item and does not require calibration.

GPS Antenna
The GPS antenna is directly connected to the navigation computer via a coaxial cable. Locations of the antenna in the vehicles are as follows:

E38: Under the rear parcel shelf.
E39 sedan: Under the rear parcel shelf.
E39 Sport Wagon: Behind the dashboard on the left side.
E46 sedan/coupe: Under the rear parcel shelf.
E46 Sport Wagon: Above the rear glass under the spoiler.
E46 Convertible: Behind the instrument cluster.
E52: Left front corner behind the dashboard.
E53: Above the rear glass under the spoiler.

Display Units
Based on the particular model, the factory installed Mk-3 system is displayed using a color board monitor or on a smaller monochromatic screen (MIR).

E52 MIR (Multi Information Radio)




E46/E53 Color Board Monitor




E38/E39 Wide Screen Color Board Monitor (phased in for E53 1/01, E46 9/01)




Navigation System Interface




Information/body bus Interface
The navigation computer is integrated into the vehicle bus system as it's main communication link with the vehicle.

Communication occurs with the following modules:
- BMBT - Control inputs
- Radio - Display data
- GM - Door open
- IKE/Kombi - On-board computer data
- Telephone PSE Box - Monitor display data, mayday function
- DISplus - Coding data

PSE = Portable Support Electronics

Video/Audio Signals

Board Monitor (Top Navigation)




The RGB video signal for all display functions of the board monitor are produced by the navigation computer graphics stage via three output signals. The Red-Green-Blue signals are direct inputs to the board monitor. The audio signals for navigation instructions to the radio are sent via two separate lines.

MIR (Radio Navigation)




Since a color display is not used for the MIR, the navigation information for the display is sent via a NAV bus. The NAV bus is a single dedicated line between the Mk-3 computer and the MIR. Audio signals for navigation instructions are sent to the radio via two separate lines.

Speed Signals
A speed signal is provided to the navigation computer for detection of distance traveled and vehicle speed to calculate the vehicles position on the digital map. The input is a processed signal provided by the vehicles DSC control unit.
- E46: The speed signal used is from the left rear wheel.
- E38/E39/E52/E53: The speed signal used is from the left front wheel.

Reverse Gear Input
The reverse gear input is used by the navigation computer to distinguish between the vehicle backing up or turning around.




- E38/E39/E52/E53: The reverse input is a high signal produced by the LCM III.




- E46: The reverse input is a high signal supplied by a splice from the back-up lights.