User's Manual
54
ABS — Antilock Brake System.
ABS Event — Impending wheel lock situation that causes the
ABS Controller to activate the modulator valve(s).
ABS Indicator Lamp — An amber lamp which indicates the
operating status of an antilock system. When the indicator lamp
is on, ABS is disabled and the vehicle reverts to normal brake
operation.
Air Gap — Distance between the Sensor and tone ring.
ASR — Automatic Slip Regulation. Another name for traction
control.
ATC — Automatic Traction Control. An additional ABS function
in which engine torque is controlled and brakes are applied
differentially to enhance vehicle traction.
ATC/ESP Lamp — A lamp that indicates when stability functions,
including traction control, roll stability program or yaw control
are operating.
Channel — A controlled wheel site.
CAN — Controller Area Network. J1939 is an SAE version of
the CAN link.
Clear Codes — System to erase historical Diagnostic Trouble
Codes (DTCs) from the ECU, from either the Diagnostic Switch
or from a hand‑held diagnostic tool (only repaired DTCs may
be cleared).
Conguration — The primary objective is to identify a “normal”
set of sensors and modulators for the Electronic Control Unit,
so that it will identify future missing sensors and modulators.
Diagnostic Connector — Diagnostic receptacle in vehicle cab
for connection of J1939 hand‑held or PC based test equipment.
The tester can initiate test sequences, and can also read system
parameters.
Diagnostic Switch — A switch used to activate blinks codes.
Differential Braking — Application of brake force to a spinning
wheel so that torque can be applied to wheels which are not
slipping.
ECU — Electronic Control Unit.
ESP — Electronic Stability Program. Full stability function that
includes RSP & YC subfunctions.
Diagnostic Trouble Code — A condition that interferes with the
generation or transmission of response or control signals in the
vehicle's ABS system that could lead to the functionality of the
ABS system becoming inoperable in whole or in part.
FMVSS-121 — Federal Motor Vehicle Safety Standard which
regulates air brake systems.
Hill Start (or “Hill Start Assist”) HS/HSA — This feature
interfaces between the transmission and braking system to help
the driver prevent the vehicle from rolling downhill when moving
up a steep incline from a stationary position.
IR — Independent Regulation. A control method in which a
wheel is controlled at optimum slip, a point where retardation
and stability are maximized. The brake pressure that is best
for the wheel in question is directed individually into each brake
chamber.
J1939 — A high speed data link used for communications
between the ABS ECU engine, transmission and retarders.
LAS — Lateral Acceleration Sensor.
MIR — Modied Independent Regulation. A method of controlling
the opposite sides of a steer axle during ABS operation so that
torque steer and stopping distance are minimized.
PLC — Power Line Carrier. The serial communication protocol
used to communicate with the trailer over the blue full time
power wire.
PMV — Pressure Modulator Valve. An air valve which is used
to vent or block air to the brake chambers to limit or reduce
brake torque.
QR — Quick Release. Quick release valves allow faster release
of air from the brake chamber after a brake application. To
balance the system, quick release valves have hold off springs
that produce higher crack pressures (when the valves open).
Relay Valve — Increases the application speed of the service
brake. Installed near brakes with larger air chambers (type 24
or 30). The treadle valve activates the relay valve with an air
signal. The relay valve then connects its supply port to its delivery
ports. Equal length air hose must connect the delivery ports of
the relay valve to the brake chambers.
Retarder Relay — A relay which is used to disable a retarder
when ABS is triggered.
RSP
— Roll Stability Program. An all‑axle ABS solution that
helps reduce vehicle speed by applying all vehicle brakes as
needed, reducing the tendency to roll over.
SAS — Steering Angle Sensor.
Sensor Clamping Sleeve — A beryllium copper sleeve which
has ngers cut into it. It is pressed between an ABS sensor and
mounting hole to hold the sensor in place.
Stored Diagnostic Trouble Codes — A DTC that occurred in
the past.
TCS — Traction Control System, another name for ATC or ASR.
TCV — Traction Control Valve.
Tone Ring — A ring that is usually pressed into a wheel hub that
has a series of teeth (usually 100) and provides actuation for the
speed sensor. Note maximum run out is .008.
YC — Yaw Control. Helps stabilize rotational dynamics of vehicle.
YRS — Yaw Rate Sensor.
GLOSSARY