Volvo VNL Service Manual page 19

Group 30 Electrical System—VNL, VNM
Sensors and senders
Many electronic signals used by ECUs and the instrument
cluster are supplied by sensors and senders. A sensor
or sender sends a signal to a control unit, or to the
microprocessor in the instrument cluster. Sensors used
in the vehicle system include the vehicle speed sensor,
the throttle position sensor and Anti-lock Brake System
(ABS) wheel speed sensors.
The vehicle speed sensor is mounted in the transmission
and reads the movement of the teeth on the output shaft. It
is of an inductive type and sends a fluctuating (sinusoidal)
signal to the engine ECU.
An Anti-lock Brake System (ABS) wheel speed sensor is
mounted in each monitored wheel. As the wheel spins,
the sensor sends a fluctuating signal to the ABS ECU,
which the ECU interprets as wheel speed.
The transmission oil temperature sender, shown in the
illustration, senses the temperature of the transmission
oil, creating a resistance and sending this signal to the
instrument cluster. The higher the temperature of the oil,
the lower the resistance, and the higher the reading shown
on the gauge.
The engine oil temperature sender functions similarly,
but sends engine oil temperature information to the
instrument cluster. The fuel sender, mounted in the fuel
tank, transmits the fuel level to the instrument cluster.
Anti-lock Brake Wheel Speed Sensor
Transmission Oil Temperature Sender
Design and Function
W5000602
W3000813
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