Navigation system

The navigation system is an optional feature of the on-board monitor system

The system is operated via the on-board monitor control panel, the navigation computer controls route planning, the acoustic indicators and visual displays are generated by the video module.

The navigation computer is connected via an ARCNET data link to the video module.

The navigation computer does not feature its own connection to the diagnostic bus so that diagnosis takes place via the ARCNET data link and the video module.

Function as of terminal R

Function

The navigation computer located in the rear of the vehicle features a CD drive, in which a CD with a digitized road map is loaded.

A GPS (satellite) receiver (GPS = global positioning system) defines the current position.

In addition, the navigation computer receives information concerning direction from a magnetic field sensor and information relating to the distance covered from the ABS control unit.

The user can enter an address via the on-board monitor operating unit. The navigation computer then uses this address to plan the most favourable route from the current location, based on certain criteria to be entered by the user (i.e. motorways, main roads, minor roads) and then highlights it visually on a road (route) map.

While driving, the navigation computer provides acoustic and visual indications relating to the proposed route dependent on the information received from the GPS, magnetic field sensor and ABS control unit, e.g. turn-off information together with the distance up to the corresponding junction or information to get into correct lane in good time, etc.

If the driver does not follow the proposed route, the navigation computer will propose an alternative route.

The system only functions in the digitized area (both detailed as well as partly mapped areas) of the map CD.

Components

Navigation computer with CD drive

The navigation control unit is accommodated together with the CD drive in one housing. The unit features an EJECT button for the CD as well as two LEDs which serve as indicators for "Power ON" and "CD in".

The current road map CD is inserted in the CD drive. The navigation system can only operate when a road map CD is inserted. The "CD in" LED on the navigation computer lights when the CD is loaded correctly. New navigation software is loaded from a software CD which is also inserted in the drive (refer to "Loading software").

Route planning takes place in the navigation computer. Relevant messages are routed via the ARCNET link to the video module which controls visual user guidance, displays visual symbols and also generates the acoustic indicators. The navigation system is operated via the On-board monitor operating unit.

The power LED lights as of terminal R provided there is no internal fault in the navigation computer and no fault on the ARCNET cable link.

The power LED flashes slowly (approx. 1 Hz) if an internal fault is detected and flashes at a fast rate (approx. 3 Hz) if there is a fault in ARCNET communication.

Map CD

The map CD contains a digitized road map.

The navigation system can only operate when a road map CD is inserted.

The digitized road map contains detailed (fully digitized) areas and partly mapped (partly digitized) areas.

• Detailed (fully digitized) areas
  All roads and additional information are indicated on the map for areas mapped in detail.
  
• Partly mapped (partly digitized) areas
  The main road network and a minimum of additional information are indicated on the map for partly mapped areas.
  

ABS control unit/speed sensor

The navigation computer receives the signals of the front right and front left speed sensors from the ABS control unit via two lines.

From these signals, the computer derives information relating to the distance covered and the changes in direction and thus coordinates the vehicle position with the map.

Magnetic field sensor

The magnetic field sensor is fitted in the rear window shelf and supplies the absolute driving direction. Its purpose is to coordinate the vehicle position with the map (mainly in curves).

Generally, care must be taken to ensure that no ferromagnetic (including umbrellas) parts are placed in the vicinity of the rear window shelf since they can impair the function of the magnetic field sensor.

GPS

The GPS (g lobal p ositioning s ystem) supplies the actual position. It consists of the satellite aerial fitted in the rear window shelf and the GPS control unit which evaluates the signals received by the aerial and calculates the current position.

The system is ready for operation as of terminal R.

If the battery is disconnected, the GPS looses all its stored information, also the position last recorded. When the battery is reconnected and terminal R is switched on, it takes approx. 15 minutes for the control unit to redefine its current position.

If the vehicle is transported over long distances with terminal R switched off (e.g. car-carrying trains), it also takes approx. 15 minutes until the current position is redefined after switching on terminal R and unrestricted satellite reception. The waiting time can be shortened by entering the new location manually.

Care must be taken to ensure that no ferromagnetic parts (including umbrellas) are placed in the area of the rear window shelf as they can influence GPS reception..

Information concerning satellite reception

The following information concerning satellite reception is possible in navigation mode:

Satellite contact is indicated in the "GPS-Logo" at the top right edge of the map display. The GPS-Logo is a small black square which, in addition to the globe symbol, the following can be displayed:

• Only the world map symbol without "GPS" lettering, without satellite symbol and without scattered white dots:
  Either the reception position is so poor that not even one satellite signal can be received (e.g. in workshop buildings). In this case, a more favourable reception position should be found.
  If this display appears permanently or more frequently although the vehicle is in a good reception position, then this indicates a fault. Troubleshooting should then be carried out in accordance with the diagnosis program after selecting the fault symptom "GPS problems".
  
• White dots scattered on black background: The number of dots is equal to the number of satellites whose signals the system can detect. This means that the basic function of the GPS is in working order. However, these signals are not sufficient to determine the exact position so that a better reception position must be found.
  
• "GPS" lettering and green satellite symbol: The received satellite signals are sufficient in order to calculate an exact position.
  

Reception may be interrupted temporarily in shadow areas obstructing the direct link between the satellite and vehicle in the form of large buildings or natural obstructions (multi-storey buildings, trees etc.). If this is the case the satellite symbol is no longer displayed in the GPS-Logo but rather only individual green dots.

Reverse signal

The navigation computer receives the "reverse" signal via the output of the light module for the right-hand reversing light.

If the lamp power circuit for the right reversing light or the lamp bulb is defective, under certain circumstances, the navigation computer will receive no signal when reverse is engaged. In this case, continue troubleshooting in the light module.

Rear window heating

Since the magnetic field generated by the rear window heating system influences the measurements of the magnetic field sensor, the navigation computer receives the information "rear window heating ON" from the air conditioning control unit via the I-bus and ARCNET cable link in order to compensate for this interfering factor in its calculations. For this reason, correct operation of the heated rear window must be ensured.

The magnetic field sensor must be recalibrated after carrying out repairs on the rear window.

Calibration

If the navigation computer or a part of the peripheral equipment was replaced, a complete or partial calibration run is necessary in order to match the peripheral equipment and computer to each other.

Precondition

• The calibration run must be carried out in the open.
  
• It must be possible to drive closed circles or loops. The diameter should be kept as small as possible and the starting and finishing points must be identical and the vehicle must be driven at slow speed (< 10 km/h) in all directions. Suitable locations are, for example, large car parks or house blocks.
  
• The calibration place must be as even as possible
  
• There must be no iron structures (e.g. crane, bridge, laden trucks), transformers, high power lines or other objects which exert magnetic influence, in the vicinity. It is also advisable to maintain a suitable distance from parked cars.
  

Note

All consumer loads such as rear window heating, air conditioning system etc. must be switched off during the calibration run.

If the site is not suitable, a corresponding message is signalled on the on-board monitor during the calibration run.

Generally applicable:

• Selection "back ": Branch back to main calibration menu without saving determined values
  
• Selection "continue ": Save determined values and branch to next step or back to main calibration menu.
  

Calibration procedure:

Instructions are displayed on the on-board monitor.

A map CD must be loaded.

If the navigation computer is new and not yet calibrated, the calibration menu is displayed immediately after selecting the navigation system.

Otherwise, the calibration menu is accessed by selecting navigation: Information - location display - press "Menu" button approx. 5 s

The calibration procedure is divided into (the individual points can be selected separately):

• Entry of vehicle data
  
• Sensor test
  
• Wheel calibration
  
• Magnetic field sensor calibration
  

Entry of vehicle data

The wheelbase and track width of the vehicle must be entered.

Sensor test

The following messages can appear on the on-board monitor during the sensor test:

• Instruction to drive in a circle.
  The circle diameter should be as small as possible. The speed must not exceed 10 km/h.
  
• Indication if driving in a circle has not been carried out correctly or the selected site is unsuitable.
  
• Error message if the navigation computer has detected a fault in the speed sensor or the magnetic field sensor.
  
• Message indicating that the navigation computer is recalibrating the magnetic field sensor.
  This procedure can eliminate positioning errors.
  

The sensor test is completed when an error message or "Calibration successful" appears.

If the sensor test was carried out as part of the troubleshooting procedure, troubleshooting should be continued after reentering the diagnosis program with "sensor test completed, continue troubleshooting".

Wheel calibration

The tyre circumference is signalled to the navigation computer during wheel calibration.

Wheel calibration is also necessary after a tyre/wheel change.

Ensure exact tyre pressure.

Procedure:

• Mark the starting point of a defined section (e.g. point, over which the centre of the rear wheel is located).
  
• Confirm with "Start" on on-board monitor.
  
• Drive over a straight distance between 4 and 6 m, the speed must not exceed 10 km/h. Take care not to brake abruptly at the end of this section. On no account reverse again.
  
• Confirm end of driven section on the on-board monitor
  
• A distance of at least 100 m must then be driven straight ahead. A corresponding message is indicated if the distance was too short or there was too much steering movement. Observe road traffic regulations.
  

Magnetic field sensor calibration

Magnetic field sensor calibration consists of 3 parts.

Part 1:

Here, the magnetic field sensor must measure all directions.

2 methods can be used for this purpose:

• Drive 2 complete circles in clockwise direction and in anticlockwise direction in order to cover all directions. A message on the on-board monitor indicates when to stop driving in a circle. This procedure is also possible on medium-sized car parks. The speed must not exceed 10 km/h.
  
• Drive several times around house blocks or similar, a complete circle need not be driven, however, all directions must be covered. A message on the on-board monitor indicates when to stop driving.
  

Part 2: Only possible after successfully completing Part 1

3 possible methods can be used (selected in menu for magnetic field sensor calibration)

• GPS calibration (time required up to 25 min)
  This method is nearly always possible, but it may be rather time-consuming.
  Ensure a clear field of vision upward, i.e. shadow areas caused by multi-storey buildings, trees etc. must be avoided.
  Drive on straight roads in all directions until sufficient directional data have been collected. A message on the on-board monitor indicates when sufficient measured data have been determined.
  Satellite contact must be made while driving (refer to description Components - GPS).
  If, after approx. 25 min driving with satellite contact, the message indicating that sufficient measured values have been recorded still does not appear on the on-board monitor, a different method should be selected or the corresponding service department should be called in.
  
• Angle calibration
  If the direction (bearing) of a longer stretch of road is known, this method requires the least amount of time.
  In this case, the geographical angle of a road is entered to a degree of accuracy of +/-1⁰ and this stretch of road is then driven.
  In Germany, the values for declination and intensity = 0.
  
• Address
  This method is only possible in the fully digitized area of the map CD.
  Here, the current location must be entered and the system proposes a stretch of road between two road junctions which must then be driven.
  

Part 3: Rear window heating (only possible after successfully completing Part 1 and Part 2)

Here, the navigation computer determines the magnetic field generated by the rear window heating system.

Procedure:

• Switch on rear window heating and enter at on-board monitor. Wait for system confirmation.
  
• Switch off rear window heating and enter at on-board monitor. Wait for system confirmation.
  

Loading software

The "load software" step must be carried out if defect code No. 22 is stored in the defect code memory or if a new navigation software version is available.

Procedure

Precondition: At least terminal R ON

• Load software CD
  The program currently running on the on-board monitor is interrupted, irrespective of whether this is the navigation program or any other program.
  
• The message "Please wait" appears on the on-board monitor after a few seconds, the software is no loaded (time required 3 min).
  
• This procedure is completed with the on-board monitor message "Software loaded successfully".
  
• The end of the procedure must then be confirmed by pressing the rotary/push-button and removing the software CD from the navigation computer.
  

Caution!

Particular care must be taken to ensure that no terminal is changed during the loading procedure. At least terminal R must be switched on for as long as software is loaded.

The navigation system in the workshop

Diagnosis

There are 3 different diagnosis programs, i.e. one for the on-board monitor operating unit, one for the video module and one for the navigation system.

To start the troubleshooting procedure, after the identification page point 1 "Start diagnosis" should be selected in the diagnosis program

In the case of fault symptoms in connection with positioning errors, a sensor test is necessary in the majority of cases, consisting of a precisely defined test run (refer to calibration run for detailed description and preconditions). This is indicated on the DIS after entering the fault symptoms.

Note

It is essential to carry out troubleshooting on the basis of symptom entry.

Read out calibration data

As of operating software status 4 or higher (indicated on the identification page of the diagnosis program), it is possible to read out the data stored in the navigation computer via diagnosis. In this way a statement can be made as to whether the calibration data are within a value range typical for E38 vehicles or not.

If operating software which features this function is loaded, the diagnosis program will contain the selection point 2 "Read calibration data" under point 3 "Service functions. After selection, information is obtained about following points:

• Navigation computer calibrated or not (all following information is only possible when computers are calibrated)
  
• Calibration of reverse signal OK. or not OK.
  
• Wheel sensor detection OK. or not OK.
  
• Sensor setting OK. or not OK.
  
• Track width within value range typical for E38 or not
  
• Wheelbase selected correctly or not
  
• Data determined during calibration of magnetic field sensor in value range typical for E38 vehicles or not
  
• Values determined during calibration of rear window heating in value range typical for E38 vehicles or not
  

If one of these values is not OK. or not within the value range typical for E38 vehicles, the diagnosis program will offer remedial measures.

It is possible that the vehicle is correctly calibrated although a calibration value is not in the value range typical for E38 vehicles. This may be the case, for example, if non-standard tyres (different track width) are fitted or if components are installed which change the magnetic field of the vehicle.