Acura TSX / Honda Accord CL. Manual - part 161

Fig. 21: Navigation System Schematic 

NAVIGATION FUNCTION 

The navigation system is composed of the navigation unit, the ECM/PCM (vehicle speed signal), the GPS 
antenna, microphone, voice control switch, audio unit, climate control unit, and the display unit.

 

2004 Acura TSX 

2004 ACCESSORIES & EQUIPMENT Navigation System - TSX

  

 

Fig. 22: Navigation Function Diagram 

VEHICLE SPEED PULSE 

The vehicle speed pulse is sent by the ECM/PCM. The ECM/PCM receives a signal from the countershaft 
speed sensor, then the processes the signal and transmits it to the speedometer and other systems. 

Fig. 23: Vehicle Speed Pulse Input 

YAW RATE-LATERAL ACCELERATION SENSOR 

The yaw rate-lateral acceleration sensor (located in the navigation unit) detects the direction change (angular 
speed) of the vehicle. The sensor is an oscillation gyro built into the navigation unit. 

SENSOR ELEMENT STRUCTURE 

 

2004 Acura TSX 

2004 ACCESSORIES & EQUIPMENT Navigation System - TSX

  

 

The sensor element is shaped like a tuning fork, and it consists of the piezoelectric parts, the metal block, and 
the support pin. There are four piezoelectric parts: one to drive the oscillators, one to monitor and maintain the 
oscillation at a regular frequency, and two to detect angular velocity. The two oscillators, which have a 90-
degree twist in the center, are connected at the bottom by the metal block and supported by the support pin. A 
detection piezoelectric part is attached to the top of each oscillator. The driving piezoelectric part is attached to 
the bottom of one oscillator, and the monitoring piezoelectric part is attached to the bottom of the other 
oscillator. 

OSCILLATION GYRO PRINCIPLES 

The piezoelectric parts have "electric/mechanical transfer characteristics." They bend vertically when voltage is 
applied to both sides of the parts, and voltage is generated between both sides of the piezoelectric parts when 
they are bent by an external force. The oscillation gyro functions by utilizing this characteristic of the 
piezoelectric parts and "Coriolis force." (Coriolis force deflects moving objects as a result of the earth's 
rotation.) In the oscillation gyro, this force moves the sensor element when angular velocity is applied. 

OPERATION 

1. The driving piezoelectric part oscillates the oscillator by repeatedly bending and returning when an AC 

voltage of 6 kHz is applied to the part, The monitoring-side oscillator resonates because it is connected to 
the driving-side oscillator by the metal block.  

2. The monitoring piezoelectric part bends in proportion to the oscillation and outputs voltage (the monitor 

signal). The navigation unit control circuit controls the drive signal to stabilize the monitor signal.  

3. When the vehicle is stopped, the detecting piezoelectric parts oscillate right and left with the oscillators, 

but no signal is output because the parts are not bent (no angular force)  

4. When the vehicle turns to the right, the sensor element moves in a circular motion with the right oscillator 

bending forward and the left oscillator bending rearward. The amount of forward/rearward bend varies 
according to the angular velocity of the vehicle.  

5. The detecting piezoelectric parts output voltage (the yaw rate signal) according to the amount of bend. 

The amount of vehicle direction change is determined by measuring this voltage.  

Fig. 24: Piezoelectric Operation 

 

2004 Acura TSX 

2004 ACCESSORIES & EQUIPMENT Navigation System - TSX

  

 

GLOBAL POSITIONING SYSTEM (GPS)

The global positioning system (GPS) enables the navigation system to determine the current position of the 
vehicle by utilizing the signals transmitted from the satellites in orbit around the earth. The satellites transmit 
the satellite identification signal, orbit information, transmission time signal, and other information. When the 
GPS receiver receives a signal from three or more satellites simultaneously, it calculates the current position of 
the vehicle based on the distance to each satellite and the satellite positions on their respective orbits. 

Fig. 25: Position Detection Image With GPS Satellite

 

2004 Acura TSX 

2004 ACCESSORIES & EQUIPMENT Navigation System - TSX