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ABS — Antilock Brake System.
ABS Event — Impending wheel lock situation that causes the
ABS controller to activate the modulator valve(s).
ABS Indicator Light — An amber light 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 Light — A light that indicates when traction control is
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 from the ECU, from either the Diagnostic Switch or from
a hand-held diagnostic tool (only repaired diagnostic trouble
codes may be cleared).
Configuration — 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 J1587 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.
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.
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.
J1587 — The SAE heavy duty standard diagnostic data link.
J1708 — An SAE standard which defines the hardware and
software protocol for implementing 9600 baud heavy vehicle
data links. J1587 version of a J1708 data link.
J1939 — A high speed 250,000 baud data link used for
communications between the ABS ECU engine, transmission
and retarders.
MIR — Modified 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.
Sensor Clamping Sleeve — A beryllium copper sleeve which
has fingers cut into it. It is pressed between an ABS sensor
and mounting hole to hold the sensor in place.
Stored Diagnostic Trouble Codes — A diagnostic trouble code
that occurred.
TCS — Traction Control System, another name for ATC or ASR.
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.
Glossary
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