earth LAND ROVER DISCOVERY 2002 Workshop Manual

INSTRUMENTS
DESCRIPTION AND OPERATION 88-9
Fuel gauge
The fuel gauge is an analogue gauge that indicates the level of fuel in the fuel tank with the ignition on. The fuel gauge
returns to 0 with ignition off. The gauge reading is proportional to the level of fuel in the tank. It is a damped action
gauge to prevent erroneous readings caused by fuel moving in the tank. The damping action is minimised when the
ignition is switched on to give an accurate reading within 2.5 seconds.
The signal input for the fuel gauge is from the tank sender unit, it is a variable voltage signal proportional to the level
of fuel in the tank. The instrument pack provides the power via fuse 27 to the fuel gauge, then from the gauge on to
the fuel tank sender unit. The earth path return circuit of the sender unit is connected to the instrument pack.
A low fuel level signal is provided for the ECM when the sender resistance is greater than 158
±8 ohms, this is used
to create a fault code indicating low fuel level during misfire diagnosis using TestBook.

INSTRUMENTS
88-10 DESCRIPTION AND OPERATION
Fuel tank sender unit
The fuel tank sender unit is combined with the pump. It contains a variable resistor with change in resistance
proportional to the change in level of fuel in the tank.
The resistance of the fuel tank sender unit in relation to tank contents and gauge display is shown in the table below:
The fuel tank sender unit input voltage feed is supplied from the fuel gauge. The earth path return circuit of the sender
unit is connected to the instrument pack.
Tank contents Sender resistance, ohms Gauge display
Empty 245 0
Full 19 1

INSTRUMENTS
DESCRIPTION AND OPERATION 88-11
Engine coolant temperature gauge
The engine coolant temperature gauge is an analogue gauge with three sections: cold temperature; normal operating
temperature; high temperature. Under normal engine operating temperatures the engine coolant temperature gauge
will display in the centre of the gauge. When the engine is cold e.g. from first start-up, the coolant temperature gauge
will display in the cold band. When the engine is over heating the temperature gauge will display in the high
temperature band. If the engine coolant temperature gauge receives no input or the input is out of range the
temperature gauge will read cold and the high coolant temperature warning lamp will be illuminated.
The input signal is a PWM signal from the engine coolant temperature sensor via the ECM. The power input for the
high coolant temperature warning lamp is supplied by the instrument pack via fuse 27. The ECM controls the earth
path to illuminate the high coolant temperature warning lamp.

INSTRUMENTS
DESCRIPTION AND OPERATION 88-15
Instrument illumination
Dimmer switch
The instrument pack contains 3 bulbs to illuminate the dials. Depending on market the bulbs are illuminated either
from the side lamps feed with no dimmer control or from a PWM dimmer control located on the dashboard. A PWM
dimmer is used so finer control of the instrument illumination can be achieved.
The input is either direct from the side lamp power feed or from the PWM dimmer control. The instrument pack
provides the earth path to illuminate the lamps.

INSTRUMENTS
88-16 DESCRIPTION AND OPERATION
Direction indicator warning lamps
The direction indicator warning lamp within the instrument pack utilises a green LED and a clear legend. The LED
flashes at the same rate as the external indicators, providing the driver with a visible warning.
Operating the left-hand indicator switch instructs the BCU to activate the left-hand indicator warning lamp.
Operating the right indicator switch instructs the BCU to activate the right-hand indicator warning lamp.
There is no self-test performed at ignition on for these warning lamps.
The power input for the LED is supplied by the instrument pack via fuse 27. The earth path for the warning lamps is
from the BCU.

INSTRUMENTS
DESCRIPTION AND OPERATION 88-17
Main beam warning lamp
The main beam warning lamp within the instrument pack utilises a clear 14 volt 2 watt long life bulb and a blue legend.
The bulb illuminates when the headlamps are switched to main beam, providing the driver with a visible warning.
There is no self-test performed at ignition on for this warning lamp.
Operating the main beam switch provides the Intelligent Driver Module (IDM) with battery voltage. This feed activates
the IDM to supply the power for the main beam warning lamp. The earth path is provided through the instrument pack.

INSTRUMENTS
88-18 DESCRIPTION AND OPERATION
Anti-lock Brake System (ABS) warning lamp
The ABS warning lamp within the instrument pack utilises an amber LED with a clear legend. If a fault within the ABS
is detected, the SLABS ECU illuminates the LED, providing the driver with a visible warning.
When the ignition is switched on, the SLABS ECU illuminates the LED to provide a self-check, providing there is no
fault it will remain illuminated for 3 seconds or until the ignition is switched off. If an ABS fault is detected while driving
the warning lamp will illuminate to alert the driver.
The power input for the LED is supplied by the instrument pack via fuse 27. The SLABS ECU provides the earth path
to illuminate the ABS warning lamp.

INSTRUMENTS
DESCRIPTION AND OPERATION 88-19
High engine coolant temperature warning lamp
The high engine coolant temperature warning lamp within the instrument pack utilises a red LED and a clear legend.
The ECM illuminates the LED when it detects the engine coolant has exceeded a temperature of 121
°C (250 °F) and
switches it off when the coolant temperature drops below 118
°C (244 °F). The ECM also illuminates the high engine
coolant temperature warning lamp when it detects the PWM duty cycle to the temperature gauge is out of range. If it
is greater than 94% duty cycle when the engine is hot, or less than 8% duty cycle when the engine is cold, the engine
coolant temperature gauge pointer will indicate cold, thus alerting the driver with an additional visible warning.
When the ignition is switched on, the ECM illuminates the LED to provide a self-check, providing there is no fault it
will remain illuminated for 3 seconds or until the ignition is switched off.
The response of the engine high temperature warning lamp varies according to engine type and market, there are
three conditions:
lV8 - Gulf.
lV8 - all markets except Gulf.
lDiesel - all markets.
The vehicle configuration determines which condition is set.
The PWM duty cycle thresholds for illuminating and extinguishing the warning lamp are given in the table below.
The power input for the LED is supplied by the instrument pack via fuse 27. The ECM controls the earth path to
illuminate the warning lamp.
Market Lamp on Lamp off
V8 - Gulf 79.8 ± 2% 77.8 ± 2%
V8 - all markets except Gulf 77.8 ± 2% 75.7 ± 2%
Diesel - all markets 78.8 ± 2% 76.8 ± 2%

INSTRUMENTS
88-20 DESCRIPTION AND OPERATION
Low fuel warning lamp
The low fuel warning lamp within the instrument pack utilises an amber LED and a clear legend. The ECM illuminates
the LED when the fuel gauge pointer has reached 8 degrees from zero. The LED remains illuminated until fuel is
added to move the fuel gauge pointer past 20 degrees from zero. This provides the driver with a visible warning that
the fuel level in the tank is low.
When the ignition is switched on, the ECM illuminates the LED to provide a self-check, providing there is no fault it
will remain illuminated for 3 seconds or until the ignition is switched off.
The sender unit resistance thresholds for switching the lamp on and off are shown in the table below:
The power input for the LED is supplied by the instrument pack via fuse 27. The ECM provides the earth path to
illuminate the warning lamp.
Lamp on Lamp off
Resistance, ohms 158 ± 8 113 ± 6
Fuel gauge pointer angle, degrees 8 20

INSTRUMENTS
DESCRIPTION AND OPERATION 88-21
Hill Descent Control (HDC) information warning lamp
The HDC information warning lamp within the instrument pack utilises a green LED and a clear legend. On vehicles
fitted with HDC, the HDC switch provides a hard wired voltage to the SLABS ECU to illuminate the LED when HDC
is switched on. This provides the driver with a visible warning that the system is enabled.
When the ignition is switched on, the SLABS ECU illuminates the LED to provide a self-check, providing there is no
fault it will remain illuminated for 3 seconds or until the ignition is switched off.
The power input for the LED is supplied by the instrument pack via fuse 27. The SLABS ECU provides the earth path
to illuminate the warning lamp.
The voltage on the SLABS ECU earth path to the instrument pack is as follows:
l< 1.8 volts = warning lamp on.
l> 7.7 volts = warning lamp off.