ignition LAND ROVER DISCOVERY 1999 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
88-12 DESCRIPTION AND OPERATION
Malfunction Indicator Lamp (MIL)/ SERVICE ENGINE SOON warning lamp
The MIL/service engine soon warning lamp within the instrument pack utilises an amber LED and a clear legend. If
an emission related fault is detected by the engine management system or, on automatic gearbox models, the EAT
ECU, the ECM will illuminate the LED providing the driver with a visible warning.
The warning lamp will illuminate whenever the vehicle is driven until the fault is repaired, and the ECM fault code
memory is cleared using TestBook.
When the ignition is switch on the ECM carries out a self-test function of the lamp. The lamp will illuminate for 3
seconds then extinguish if no faults exist. If a fault is present the lamp will be extinguished for 1 second before
illuminating again to indicate a fault exists.
There are two configurations of the legend for the warning lamp:
lNAS and Canada = SERVICE ENGINE SOON text.
lAll other markets = MIL SAE J1930 symbol.
The power input for the LED is supplied by the instrument pack via fuse 27. The ECM provides a voltage to the
instrument pack Central Processing Unit (CPU) to control the warning lamp:
l< 1.8 volts = warning lamp on.
l> 7.7 volts = warning lamp off.

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.

INSTRUMENTS
88-22 DESCRIPTION AND OPERATION
Brake system warning lamp
The brake system warning lamp within the instrument pack utilises a red LED and a clear legend. If the brake fluid
level is low, the hand brake is operated or there is a brake system fault, the LED will be illuminated providing the driver
with a visible warning.
When the ignition is switched on, the instrument pack 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.
There are two configurations of the legend for the warning lamp:
lNAS only.
lAll other markets.
The power input for the LED is supplied by the instrument pack via fuse 27. The hand brake switch, the low brake fluid
level switch or the SLABS ECU provides the earth path illuminating the warning lamp.
The hand brake switch has a separate connection to the vehicle body. The low brake fluid switch connects to an earth
header joint.
On the earth paths to the instrument pack the warning lamp is controlled according to these voltages:
l< 1.8 volts = warning lamp on.
l> 7.7 volts = warning lamp off.

INSTRUMENTS
DESCRIPTION AND OPERATION 88-23
Differential lock warning lamp (If fitted)
The differential lock is a device used for rolling road testing only on vehicles up to 03 model year. On vehicles from
03 model year, the differential is a driver selectable option which can also be used for off road driving. Refer to the
service procedures for details of rolling road testing on vehicles up to and from 03 model year.
CAUTION: Engage the differential lock when testing the vehicle on a two wheel rolling road. The propeller
shaft connecting the axle not on the rolling road must also be removed.
Differential lock warning lamp – vehicles up to 03 model year
The differential lock warning lamp within the instrument pack utilises a red LED and a clear legend. When the
differential lock is engaged, using the lever on the side of the transfer box, the differential lock switch is operated and
the warning lamp is switched on providing the driver with a visible warning.
When the differential lock is engaged, the warning lamp will be illuminated continuously when the ignition switch is in
position II.
Differential lock warning lamp – vehicles from 03 model year
The differential lock warning lamp is located in the top left hand corner of the instrument pack and uses an amber LED
and a clear legend. When the differential lock is engaged, the warning lamp illuminates when the ignition is on to
provide a visual indication to the driver that the differential lock is engaged. The instrument pack, simultaneously emits
three audible warning chimes as a confirmation.
When the differential lock is disengaged, the warning lamp is extinguished and the instrument pack simultaneously
emits three audible warning chimes as a confirmation.
All vehicles
The power input for the LED is supplied by the instrument pack via fuse 13 in the engine compartment fusebox. The
differential lock switch or switches provide(s) the earth path illuminating the warning lamp.
The voltage on the differential lock switch or switches to instrument pack earth path produces the following warning
lamp functions:
l< 1.8 volts = warning lamp on.
l> 7.7 volts = warning lamp off.