Toyota COMPUTER-CONTROLLED SYSTEM User Manual

ELECTRONIC CONTROL SYSTEM
- Vehicle Speed Senso r
VEHICLE SPEED SENSO
R
This sensor senses the actual speed at which the
vehicle is traveling . It outputs an SPD signal,
which is used mainly to control the ISC system,
and to control the air-fuel ratio during
acceleration, deceleration, etc
.
There are four types of speed sensor :
• Reed switch type
• Photocoupler typ e
• Electromagnetic pickup typ
e
• MRE (magnetic resistance element) typ
e
1 . REED SWITCH TYP E
This sensor is mounted in the analog
combination meter . It contains a magnet which
is rotated by the speedometer cable, turning the
reed switch on and off . The reed switch goes on
and off four times each time the speedometer
cable rotates once .
The magnet has the polarities shown in the
figure below . The magnetic force at the four
areas of transition between the N and S poles of
the magnet opens and closes the contacts of the
reed switch as the magnet rotates .
Q To speedometer cabl
e
OHP 2
9
ELECTRICAL CIRCUITRY
Engine ECU
2
. PHOTOCOUPLER TYP E
This sensor is mounted in the combination
meter
. It includes a photocoupler made from an
LED, which is aimed at a phototransistor . The
LED and phototransistor are separated by a
slotted wheel, which is driven by the
speedometer cable
. The slots in the slotted
wheel generate light pulses as the wheel turns,
with the light emitted by the LED divided into 20
pulses for each revolution of the cable
. These 20
pulses are converted to four pulses by the digital
meter computer, then sent as signals to the ECU .
Slo tt ed
wheel
OHP 29
ELECTRICAL CIRCUITR Y
+B
Combination
meter Puls
e
Phototransistor
conversio n
circuit
Engine EC U
OHP 2 9
34 OHP 29

Toyota COMPUTER-CONTROLLED SYSTEM Specifications

General

Brand	Toyota
Model	COMPUTER-CONTROLLED SYSTEM
Category	Automobile Accessories
Language	English