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
1 Warning switch
2 Handbrake lever
3 Cable
4 Protective sleeve
5 Drum brake
6 'C' clip
7 Threaded sleeve
8 Adjuster wheel
9 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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