Glossary
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
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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
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.
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.
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