Brakes (Description): Description and operation

Description

General

Vehicle braking is provided by disc brakes on the front wheels and drum brakes on the rear wheels. The foot brakes are operated by a diagonally split, dual circuit hydraulic system with vacuum servo power assistance. A cable operated handbrake operates on the two rear brakes.

The ABS features 4-wheel electronic traction control and hill descent functions as well as anti-lock braking and electronic brake distribution.

Slip Control System

Freelander incorporates an electronic slip control system. Up to 2001 MY, this consists of a TEVES Mk 20 ABS modulator and passive ABS sensors. From 2002 MY onwards, a TEVES Mk 25 ABS modulator and active ABS sensors are installed. Both systems incorporate the same features, as follows: l Anti-lock braking system l Hill descent control l Electronic traction control l Electrical brake-force distribution l CAN communication link

Both systems communicate via CAN with the Engine Control Module (ECM), the instrument pack and, on automatic derivatives, with the Electronic Automatic Transmission (EAT) ECU. The systems comprise the following components: l Electronic control unit l Modulator l ABS sensors l Mechanical brake switch l Brake fluid level switch l HDC relay and switch l Accelerometer

Electronic Control Unit The Electronic Control Unit (ECU) determines the speed and acceleration of each wheel, controls appropriate hydraulic functions and monitors system operation for fault conditions and interfaces to other vehicle systems. The ECU is attached to the Modulator unit and is mounted underbonnet on the RHS valence behind the headlamp.

Under the following conditions the ECU is programmed to switch off the main software driver which will result in the illumination and disabling of the ABS, TC, HDC and EBD warning lamps: l If the IGN voltage drops to values, which are not sufficient to maintain a stabilised, supply voltage for the processors. This voltage is below the functional operating voltage of 8 volts. The controller will invariably switch on again when the minimum operating voltage of 10 volts is reached. l If the following failures or errors are detected: l Valve failure l Failure of two ABS sensors l Main driver failure l Redundancy error l Over voltage

The ECU will also inhibit the ABS function, traction control, hill descent control and illuminate their respective warning lamps without switching off the main driver in the following circumstances: l Ignition voltage supplied to the ABS ECU < 8 volts l Failure of one or more of the ABS sensors l Pump motor failure

If there is a CAN error message from the ECM or the EAT ECU, or if there is a brake pedal switch fault, the ABS ECU disables the ETC and HDC functions and illuminates the related warning lamps.