Discovery 2. Manual - part 212

 

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Discovery 2. Manual - part 212

 

 

BRAKES

DESCRIPTION AND OPERATION

70-23

Typical disabled times

Diagnostics
While the ignition is on, the diagnostics function of the SLABS ECU monitors the system for faults. In addition, the 
return pump is tested by pulsing it briefly immediately after the engine starts provided vehicle speed exceeded 4.4 
mph (7 km/h) during the previous ignition cycle. If a fault exists in a warning lamp circuit, the lamp will not illuminate 
during the lamp check at ignition on but, provided there are no other faults, the related function will otherwise be fully 
operational. If a fault is detected during the power up, the SLABS ECU stores a related fault code in memory and 
illuminates the appropriate fault warning lamps. If a fault is detected later in the drive cycle, the SLABS ECU also 
sounds the audible warning three times.

Fault codes and diagnostic routines can be accessed by connecting Testbook to the vehicle's diagnostic connector 
in the driver's footwell.

Warning lamp fault operation

After detecting a fault, the SLABS ECU selects an appropriate default strategy which, where possible, retains some 
operational capability. A shuttle valve switch fault and throttle position signal fault are classified as permanent faults. 
If a permanent fault is detected, the related warning lamp illumination and default strategies are automatically 
employed in subsequent ignition cycles, even if the fault is intermittent, until the fault has been rectified and cleared 
from memory. If a non permanent fault is detected, the related warning lamp illumination and default strategies will 
only be employed in subsequent ignition cycles if the fault is still present.

After rectification of an ABS sensor fault, the ABS and ETC functions are disabled, and the ABS warning lamp remains 
illuminated after the lamp check, until vehicle speed exceeds 9.4 mph (15 km/h) (to allow additional checks to be 
performed).

Vehicle speed, mph (km/h)

Time, minutes

1.3 (2)

40

12.5 (20)

33

15.6 (25)

17

25.0 (40)

9

31.3 (50)

6

Item

Check

Warning lamp

ABS

Brake

ETC

HDC 
fault

ABS sensors

Resistance (to check status)

On

On

On

On

Brake lamps relay

Open/Short circuit

Off

Off

Off

On

Engine data

Sticking throttle, signal failure, data corruption

Off

Off

On

On

Inlet solenoid valves

Open/Short circuit

On

On

On

On

Outlet solenoid valves

Open/Short circuit

On

On

On

On

Reference earth

Connection to earth

On

On

On

On

Return pump monitor

Correct pump operation

On

On

On

On

Return pump relay

Open/Short circuit

On

On

On

On

Shuttle valve switches

Open/Short circuit

On

On

On

On

SLABS ECU

Internal failure

On

On

On

On

Supply voltages

Range (10 to 16 V)

On

On

On

On

BRAKES

70-24

DESCRIPTION AND OPERATION

Default strategies

Electrical data
Nominal resistance values for applicable brake control components are as detailed below:

Fault

Default strategy

Brake lamps relay

ABS: Enabled.
ETC: Enabled.
EBD: Enabled.
HDC: Enabled.

Throttle position signal failure

ABS: Enabled.
ETC: Disabled.
EBD: Enabled.
HDC: Immediately disabled if not in active braking mode; faded out then disabled if in active 
braking mode.

No reference earth

ABS: Disabled.
ETC: Disabled.
EBD: Partly disabled.
HDC: Disabled.

Return pump or relay fault

ABS: Disabled.
ETC: Disabled.
EBD: Partly disabled.
HDC: Disabled.

Shuttle valve switch failure

ABS: Deceleration threshold increased; return pump activated if sum of output valve 
actuation on one axle exceeds 140 milliseconds.
ETC: Disabled.
EBD: Inlet valves of rear axle close at vehicle deceleration rates of  0.3 g and above.
HDC: Disabled.

SLABS ECU internal failure

ABS: Disabled.
ETC: Disabled.
EBD: Disabled.
HDC: Disabled.

Supply voltage out of limits

ABS: Disabled.
ETC: Disabled.
EBD: Disabled.
HDC: Disabled.

Component

Resistance, ohms

Brake lamp relay coil

117 - 143

Return pump relay coil

82.8 - 101.2

ABS sensor

950 - 1100

Shuttle valve switches, both open (brakes off)

2977 - 3067

Shuttle valve switches, both closed (brakes on)

1007 - 1037

Shuttle valve switches, one open, one closed

1992 - 2052

Inlet solenoid valve

5.9 - 7.3

Outlet solenoid valve

3.0 - 3.6

BRAKES

DESCRIPTION AND OPERATION

70-25

DESCRIPTION AND OPERATION

Handbrake component layout

Warning switch
Handbrake lever
Cable
Protective sleeve
Drum brake

'C' clip
Threaded sleeve
Adjuster wheel
Base plate

10 Transmission tunnel

BRAKES

70-26

DESCRIPTION AND OPERATION

Description

General
The handbrake consists of a drum brake, installed on the rear of the transfer box, operated by a cable connected to 
a handbrake lever between the front seats.

Handbrake lever
The handbrake lever is mounted on a base plate which attaches to the transmission tunnel. A conventional ratchet 
and thumb operated release button are incorporated for locking and unlocking the lever. A warning switch on the base 
of the lever operates the brake warning lamp in the instrument pack. While the handbrake is applied the warning 
switch connects an earth to the instrument pack which, if the ignition is on, illuminates the brake warning lamp. In 
some markets, the instrument pack performs a bulb check of the brake warning lamp each time the ignition is switched 
on.

Cable
The handbrake cable consists of inner and outer cables installed between the handbrake lever and the drum brake. 
A protective sleeve is installed on the cable to protect the cable from heat from the exhaust system. Handbrake 
adjustment is provided by a threaded sleeve installed on the outer cable where it locates in the handbrake lever. 
Turning an adjuster wheel, which is keyed to the threaded sleeve and secured by a 'C' clip, alters the effective length 
of the outer sleeve and consequently changes the handbrake lever movement needed to apply the drum brake.

 

 

 

 

 

 

 

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