Bendix Commercial Vehicle Systems TABS-6 ADVANCED MC SD SHEET - Manual (Page 3)

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3. ANTILOCK BRAKE SYSTEM
(ABS) OPERATION
The Bendix ® TABS‑6 ™ Adv MC module uses wheel speed
sensors, modulator relay valves (MRVs); and an ECU to
optimize the contact between the tires and the road surface
during a braking event where excessive wheel slip — or
wheel lock‑up — is detected.
When a situation is detected where the system needs
to intervene, the ECU will activate the MRVs to apply
controlled brake pressure at the wheel ends. Depending on
the configuration of the ABS system, interventions may be
made on individual wheels, or pairs of wheels. In the case
of pairs of wheels, the wheels controlled by a modulator
may be either on the same side of the vehicle, or at both
ends of an axle.
The TABS-6 Adv MC module ECU is able to modulate the
brake pressure with greater speed and accuracy than a
driver.
Normal Braking
During normal braking the TABS-6 Adv MC module
functions as a standard relay valve. If the ECU does not
detect excessive wheel slip, it will not activate the ABS
system, and the vehicle will stop with normal braking.
Side Control (Independent Control)
Side control uses a single modulator relay valve to sepa‑
rately control the braking on one or more wheels, on each
side of the vehicle.
In the case of braking surfaces with poor overall traction,
the side control ABS interventions will maintain the wheels
on each side of the vehicle independently, at just under the
speed where they would lock up.
Axle Control
Axle control uses a single modulator relay valve to control
the wheels at both ends of a given axle (or multiple axles
in cases where a single MRV is controlling several axles).
In the case of braking surfaces with poor overall traction
(e.g. roads that are worn, slippery, or are made of loose
gravel) — or braking surfaces with areas of poor traction
(e.g. asphalt roads with patches of ice) — axle control ABS
interventions will maintain the wheel that is not slipping at
just under the speed that will lock the wheel. The system
permits the other wheel (that is experiencing slippage)
temporary periods of wheel‑lock during the intervention.
Axle control should not be used on 5th wheel dollies or
steerable axles.
When intervening on regular traction road surfaces, a
system configured for axle control performs similar to a
side control, two‑modulator system.
ABS Fail‑Safe
The Bendix ® TABS‑6 ™ Adv MC module is designed to react
in a fail-safe manner in the event of a system Diagnostic
Trouble Code (DTC). For example, if the ECU detects that
a sensor is not responding, an ABS system DTC will be set
and the TABS‑6 Adv MC module will illuminate the trailer
ABS indicator lamp and revert to a fail‑safe mode where
some, or all, Advanced ABS functions (including TRSP)
may not function. Even in cases where the ABS system
is completely disabled, the standard pneumatic brake
function of the vehicle will still be available, but without the
benefits of ABS. The TRSP feature is also disabled with an
active ABS system diagnostic code. If the indicator lamp
is illuminated, always have the ABS system serviced at the
earliest opportunity.
1
21
22
22 21
21
42
22
1/2" NPT Supply
Port 1
Two 3/8" NPT Delivery
Ports 22
(To Brake Chambers)
Two 3/8" NPT Delivery
Ports 21
(To Brake Chambers)
3/8" NPT Control Port
with Integral Filter
3/8" NPT Load Port 42
For Air Suspension
(Plugged for Non-Air Suspension or
Spring Suspension Sensor Vehicles)
3/8" NPT Delivery
Port 21
(to Brake Chambers)
3/8" NPT Delivery
Port 22
(to Brake Chambers)
FIGURE 2 ‑ PoRtS uSed