Operation CHARM: Car repair manuals for everyone.
Home >> Land Rover >> 2005 >> LR3 (LA) V8-4394cc 4.4L >> Repair and Diagnosis >> Brakes and Traction Control >> Parking Brake System >> Description and Operation >> Part 1

Part 1



Parking Brake And Actuation

OPERATION

Power Distribution
Feed from the positive battery terminal (C0192) is supplied to fusible link 8E and fusible link 11E (C0632) on an R wire. Both are located in the Battery Junction Box (BJB). Fusible link 8E (C0570) provides a constant battery feed to the parking brake module (C2178) on a GY wire. The module (C2178) is provided a ground on a pair of B wires.

Fusible link 11E (C0570) is connected to the ignition switch (C0028) by an N wire. When the key is placed in the ignition switch, current flows across the switch (C0028) to fuse 40P (C0582) on an LGW wire. Fuse 40P (C0586) is located in the Central Junction Box (CJB) and provides a 'key in' signal to the parking brake module (C2178) on an LGW wire.

When the key is turned to the 'auxiliary' position, current flows across the ignition switch (C0028) to the CJB (C0582) on a W wire. When the key is turned to the 'ignition' position, current flows across the ignition switch (C0028) to fuse 41P and the CJB (C0582) on a Y wire. Fuse 41P (C0585) provides an ignition feed to the parking brake module (C2178) on an R wire.

Parking Brake Switch
The parking brake switch contains four micro switches. These are activated by the handle of the parking brake switch. The parking brake module (C2178) monitors the condition of the micro switches within the parking brake switch (C2180) as follows:

Apply
When the switch is pulled up to apply the parking brake, micro switch 2 closes. The parking brake module is connected to micro switch 2 by an R wire. When the micro switch closes, a signal is returned to the parking brake module via micro switch 5 on a YG wire.

Release
When the switch is pushed down to release the parking brake, micro switch 1 and micro switch 4 close. The parking brake module is connected to micro switch 1 by a YU wire and micro switch 4 by a Y wire. When the micro switches close, a signal is returned to the parking brake module via micro switch 5 on a YG wire.

Clutch Pedal Position Sensor

NOTE: The clutch pedal position sensor is fitted to vehicles with manual transmission only.

The clutch pedal position sensor is a Hall effect sensor. The signal supplied by the sensor enables the parking brake module to learn the travel range of the clutch pedal. The parking brake module then adopts a point 20% before the upper threshold of the travel range as the point at which the clutch begins to engage. This is used as the reference point for the Drive Away Release (DAR) function.

The parking brake module (C2178) provides a signal feed to the clutch pedal position sensor (C0667) on a W wire and a ground path via an R wire. The sensor returns a clutch pedal position signal to the parking brake module on a U wire.

Instrument Cluster
The parking brake has two warning indicators located in the speedometer of the instrument cluster (C0230). These are controlled by the parking brake module (C2178) via the high speed CAN bus on YN (high) and YB (low) wires.

There is also a hard wired connection between the parking brake module (C2178) and the instrument cluster (C0230) via a G wire. This enables the parking brake module to illuminate the red warning indicator when the CAN bus has powered down.

CAN Bus
The parking brake module (C2178) uses the high speed CAN bus to communicate with the following components and systems on YN (high) and YB (low) wires.
^ The rear differential control module (C2162).
^ The Engine Control Module (ECM) (C0872 on TdV6 vehicles, C0635 on V6 and V8 petrol vehicles).
^ The air suspension control module (C0867).
^ The transfer box control module (C1854).
^ The ABS module (C0506).
^ The transmission control module (C0193).
Parking Brake





COMPONENT LOCATIONS

GENERAL
The parking brake is an electrically actuated system that operates drum brakes integrated into the rear brake discs. The parking brake system consists of:

^ A parking brake switch.
^ Left and right drum brakes.
^ Left and right brake cables.
^ An emergency release cable.
^ A clutch pedal position sensor (manual transmission models only).
^ Two parking brake indicators.
^ A parking brake module.

The parking brake is operated by the parking brake module, which adjusts the tension of the brake cables to apply and release the drum brakes. Operation of the parking brake module is initiated by the parking brake switch.

PARKING BRAKE SWITCH





The parking brake switch is used by the driver to apply and release the parking brake, and is installed in the center console adjacent to the gear lever.

Slots on the sides of the parking brake switch engage with the top panel of the center console, and a screw secures the parking brake switch in position. An electrical connector on the back of the switch provides the interface with the vehicle wiring. A brake symbol on the switch illuminates when the exterior lamps are selected on.

There are three states for the parking brake switch:
^ Apply request, when the handle of the parking brake switch is pulled up.
^ Release request, when the handle of the parking brake switch is pushed down.
^ Idle, when the handle of the parking brake switch is in the central or rest position.

Micro switches, incorporated into the parking brake switch, are activated by the handle of the parking brake switch. To determine the operating state of the parking brake switch, the parking brake module scans the circuits containing the micro switches.

DRUM BRAKES

NOTE: RH brake shown, LH brake similar





Each drum brake consists of a pair of brake shoes installed on a backplate attached to the rear hub carrier. The brake shoes operate on the drum integrated into the rear brake disc. The orientation of the brake shoes differ by 180' between the LH and RH brakes.

When the parking brake module tensions the brake cables, the movement is transmitted to an operating lever on one of the brake shoes. The operating lever pivots against a cross strut, which forces the brake shoes apart and into contact with the drum in the rear brake disc. Brake shoe to drum clearance is set with two manual adjusters, which are accessed through a hole in the brake disc. One of the adjusters is a conventional toothed wheel adjuster. The second adjuster is a wedge adjuster operated by an Allen screw.

After replacement of the brake shoes or brake discs, a bedding in procedure must be performed to ensure the drum brakes operate satisfactorily.

Prior to removing a brake disc from a vehicle, power should be disconnected from the parking brake module. Operation of the parking brake switch while a brake disc is removed can cause the actuating mechanism in the parking brake module to seize.

BRAKE CABLES








The brake cables consist of Bowden cables installed between the parking brake module and the drum brakes. Nuts, on the ends of the outer cables, secure the brake cables to the parking brake module and the backplate of the related drum brake. In each drum brake, the inner cable is located in the guide spring and connected to the brake shoe operating lever by a nipple on the end of the cable. In the parking brake module, the two inner cables are joined together via the force sensor and the spline shaft.

The inner cable of the RH brake cable is connected to a nipple on the force sensor by a 'shoe' on the end of the cable, a locking cover keeps the shoe engaged with the nipple.

The inner cable of the LH brake cable is connected to the spline shaft by a threaded connector (LH thread); a squared flange at the end of the threaded connector locates in the housing of the parking brake module, to prevent the threaded connector from turning with the spline shaft.

When the spline shaft turns, the threaded connector of the LH brake cable is screwed into or out of the spline shaft, which changes the effective length of the inner cables and operates the drum brakes. The ability of the spline shaft to move axially in the gearbox equalizes the load applied by the inner cables to the two drum brakes.

Prior to disconnecting a brake cable, power should be disconnected from the parking brake module. Operation of the parking brake switch while a brake cable is disconnected can cause the actuating mechanism in the parking brake module to seize. In addition, the parking brake may not switch off until 20 minutes after key-off. Automatic re-apply cannot be eliminated until this period has expired.

pro multis · About Operation CHARM