Number of satellites



2 or less

Measurement impossible

Vehicle position cannot be obtained because the number of satellites is not enough.


2-dimensional measurement is possible

Vehicle position is obtained based on the current longitude and latitude. (This is less precise than 3-dimensional measurement.)


3-dimensional measurement is possible

Vehicle position is obtained based on the current longitude, latitude and altitude.

(d) Map matching

The current driving route is calculated by autonomous navigation (according to the gyro sensor and vehicle speed sensor) and GPS navigation. This information is then compared with possible road shapes from the map data in the map disc and the vehicle position is set onto the most appropriate road.




The system compares the shape of the roads L1, L2 and L3 to the estimated running track after the vehicle makes a right turn. At point A, the vehicle position differs enough from the shape of L1 that the display switches to the road L2.


2. DVD (Digital Versatile Disc) player outline (for navigation map)

(a) The navigation ECU uses a laser pickup to read the digital signals recorded on a DVD. HINT:

• Do not disassemble any part of the navigation ECU.

• Do not apply oil to the navigation ECU.

• Do not insert anything but a DVD into the navigation ECU.


Do not look directly at the laser pickup because the navigation system uses an invisible laser beam.

Be sure to only operate the navigation system as instructed.

3. AVC-LAN Description

AVC-LAN, an abbreviation for "Audio Visual Communication Local Area Network", is a united standard developed by the manufacturers in affiliation with Toyota Motor Corporation. This standard pertains to audio and visual signals as well as switch and communication signals.


Radio Receiver (Resistor 60 to 80 Q)


Stereo Component Amplifier

Recently, car audio systems have rapidly developed and the functions have vastly changed. The conventional car audio system is being integrated with multi-media interfaces similar to those in navigation systems. At the same time, customers are demanding higher quality from their audio systems. This is merely an overview of the standardization background. The specific purposes are as follows.

(1) To solve sound problems, etc. caused by using components of different manufacturers through signal standardization.

(2) To allow each manufacturer to concentrate on developing products they do best. From this, reasonably priced products can be produced.


• If a short to +B or short to ground is detected in the AVC-LAN circuit, communication is interrupted and the audio system will stop functioning.

• If an audio system is equipped with a navigation system, the multi-display unit acts as the master unit.

If the navigation system is not equipped, the audio head unit acts as the master unit instead. If the radio and navigation assembly is equipped, it is the master unit.

• The radio receiver provides resistance to make communication possible.

• The car audio system with an AVC-LAN circuit has a diagnostic function.

• Each component has a specified number (3-digit) called a physical address. Each function has a number (2-digit) called a logical address.

4. Communication system outline

(a) Components of the navigation system communicate with each other via the AVC-LAN.

(b) The radio receiver has enough resistance (60 to 80 Q) necessary for communication.

(c) If a short circuit or open circuit occurs in the AVC-LAN circuit, communication is interrupted and the navigation system will stop functioning.

5. Diagnostic function outline

(a) The audio system has a diagnostic function (the result is indicated on the master unit).

(b) A 3-digit hexadecimal component code (physical address) is allocated to each component on the AVC-LAN. Using this code, the component in the diagnostic function can be displayed.

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