Honda 2004 Odyssey Service Manual page 1256

Wheel Sensors
The wheel sensors are the magnetic contactless type. As the gear pulser teeth rotate past the wheel sensor's magnetic
coil, AC current is generated. The AC frequency changes in accordance with the wheel speed. The ABS control unit
detects the wheel sensor signal frequency and thereby detects the wheel speed.
GEAR PULSER
Wheel Speed and Modulator Control
SPEED
PRESSURE
OUTLET
VALVE
ON
OFF
INLET
VALVE ON
OFF
MOTOR
ON
OFF
When the wheel speed drops sharply below the vehicle speed, the inlet valve closes and if necessary the outlet valve
opens momentarily to reduce the caliper fluid pressure. The pump motor starts at this time. As the wheel speed is
restored, the outlet valve closes, and the inlet valve opens momentarily to increase the caliper fluid pressure.
WHEEL SENSOR
VEHICLE SPEED
REEFRENCE VEHICLE SPEED
at HIGH SPEED
at LOW SPEED
WHEEL SPEED
TIME
19-55