GMC chevrolet camaro 2000 Service Manual page 723

5-250 Antilock Brake System
ABS Valves
The ABS valves decrease or. maintain brake fluid
pressure at the individual wheel circuits. If the vehicle
is not equipped with traction control there are
three Inlet, and three Outlet solenoid valves. If the
vehicle is equipped with traction control there
are four Inlet, and four Outlet solenoid valves. The
solenoid valves maintain, increase, or decrease brake
fluid pressure to the individual wheel circuits. The
EBCM/EBTCM commands the valves to their correct
position during an antilock or traction event. During
antilock mode, the pressure in each hydraulic
circuit can be held or released by activating the
appropriate valves. The normal state of the inlet valves
is open, while the normal state of the Outlet valves
is closed. This allows direct master cylinder pressure
to the brakes during normal braking. The ABS
valves are located within the BPMV and are not
serviced separately.
TCS Master Cylinder Isolation Valves
If the vehicle is equipped with Traction Control there is
one TCS Master Cylinder Isolation Valve within the
BPMV. This valves isolates the master cylinder so the
pump motor can build brake fluid pressure for the
rear brakes during a traction event.
TCS Prime Valves
If the vehicle is equipped with Traction Control there is
one TCS prime valve within the BPMV. This valves
allow the pump to draw fluid from the master cylinder
reservoir, through the compensating ports in the
master cylinder bore.
Electronic Brake And Traction Control Module
The EBCM/EBTCM performs the following primary
functions:
., Detects wheel slip tendencies
" Detects wheel speed differences
" Controls the brake system while in the antilock or
traction control mode
.. Controls the Electronic Brakeforce
Distribution (EBD)
• Monitors the system for proper electrical operation
Brakes
The EBCM/EBTCM also controls the display of the
ABS and traction control DTCs while in diagnostic
mode. The EBCM/EBTCM continuously checks
the speed of each wheel in order to determine if any
wheel is beginning to slip. If a wheel slip tendency
is detected, the EBCM/EBTCM commands the
appropriate valve positions to modulate the brake fluid
pressure in some or all of the hydraulic circuits.
This action prevents wheel slip and provides optimum
braking. The EBCM/EBTCM continues to control
pressure in the individual hydraulic circuits until
a slipping tendency is no longer present. The
EBCM/EBTCM continuously monitors the ABS/TCS for
proper operation. If an error is detected, the
EBCM/EBTCM can disable the ABS/TCS and turn on
the ABS or TCS OFF Indicators in the IPC.
Wheel Speed Sensors
A wheel speed sensor is located at each front wheel
bearing assembly. If the vehicle is equipped with
traction control a wheel speed sensor i~ located at each
rear wheel bearing assembly. If the vehicle is not
equipped with traction control then a single rear wheel
speed sensor is located in the differential housing. The
sensors use AC voltage in order to transmit wheel
speed information to the EBCM/EBTCM. Passing a
toothed sensor ring past a stationary sensor causes the
magnetic induction that generates the voltage. A pair of
wires carries the signal to the EBCM/EBTCM. The
wheel speed sensors are located in their respective
assemblies and are not adjustable.
Traction Control System ON/OFF Switch
The Traction Control On/Off Switch is a momentary on
switch that allows the driver to shut off the TCS for
personal or diagnostic reasons. Turning the switch to
off places the TCS in the passive mode while
maintaining ABS functions. With the TCS system on,
pressing the switch disables the T.CS and the
TRACTION OFF indicator turns on.
Stoplamp Switch
The stoplamp switch is an inputto the EBCM/EBTCM.
The EBCM/EBTCM uses the stoplamp switch in
order to tell when the brake pedal is being applied.
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