Subaru 2002 Impreza Service Manual page 446

3
COMBINATION METER
Instrumentation/Driver Info
2. OPERATION
As the driven key rotates, the magnet turns causing the magnetic field of the Hall IC to change.
The Hall IC generates a signal that corresponds to a change in the magnetic field.
One turn of the driven key in the speed sensor sends 4 pulses to the combination meter, engine
control module and cruise control module.
Signal (4 pulses
per revolution)
Low
speed
High speed
Revolution of
transmission
+
output gear
Vehicle speed
I
IG
A
sensor
Combination meter
-
Speedometer
drive circuit
Odometer and
tripmeter drive
circuit
I - ,
Engine control module
Cruise control module
NF0268
E: TACHOMETER
The tachometer drive circuit is connected to the engine speed sensing circuit in the engine control
module.
When the engine speed increases or decreases, the voltage of the circuit also increases or de-
creases, changing the magnetic force of the tachometer drive coil.
The tachometer needle then moves in accordance with change in the engine speed.
Combination meter
1
. . - . . - . . - . . - . .
I--
:
Tachometer drive circuit
ECM
- -
NF0269
IDI-9