Part 1
Instrument Cluster
INSTRUMENT CLUSTER
NOTE: TDV8 Shown
INSTRUMENT CLUSTER - NAS ONLY
General
The instrument clusters fitted to all Range Rover models are similar and only differ in the following features:
- mph or km/h speedometer
- tachometer maximum rev/min band
- mph or km/h odometer and trip display
- message center language display
- warning indicators applicable to model/market
- ambient temperature display degree C or degree F.
The instrument cluster is a totally electronic device which receives analogue or digital signals via hardwired or bus
The signals are processed by processors which transpose the data into analogue gauge indications or warning lamp illumination. The cluster is connected to the vehicle electrical system by two connectors which provide all input and output connections for instrument cluster operation.
No components of the instrument cluster are serviceable.
The instrument cluster has two main functions; to provide information to the driver of the vehicle status and to process and relay digital signals from and to other system controlling modules.
The instrument cluster features the following displays:
- Tachometer - large analogue display
- Speedometer - large analogue display
- Fuel level gage - small analogue display
- Engine coolant temperature gage - small analogue display
- Engine service data - Message center LCD (liquid crystal display)
- Transmission/transfer box status indicator - LED (light emitting diode) illuminated
- Odometer - LCD (liquid crystal display)
- Trip meter - LCD (liquid crystal display)
- Ambient temperature - Message center LCD (liquid crystal display)
- Sounder - audible warning chimes
- Message center.
The instrument cluster also features a number of warning indicators. The warning indicators illuminate in one of four colors which indicate the level of importance of the warning as follows:
- Red = Warning
- Amber = Caution
- Green = System operative
- Blue = Headlamp high beam operative.
WARNING INDICATORS
The warning indicators are located in two groups at the left and right hand side of the cluster. The turn signal indicators and high beam warning indicators are located at the top of the display and the glow plug, DSC and HDC warning indicators are located above the message center, between the two large analogue gauges.
The warning indicators can be split into two groups; self controlled and externally controlled.
Self controlled indicators are dependant on software logic within the instrument cluster for activation. The cluster software controls the indicator check illumination at ignition on and all indicators whose operation is wholly controlled by the cluster, the low fuel level warning indicator for example.
Externally controlled indicators are supplied with a current from another system controlling module or triggered by the cluster on receipt of a bus message from another system module.
Some indicators are activated by an external system module, but the control logic is retained within the cluster. For example, the turn signal indicator lamps are synchronized and controlled by the LCM (lighting control module), but the indicator illumination logic is retained within the cluster. These indicators are shown in the following table as being self and externally controlled.
The following table shows the available indicator lamps and indicates if they are subject to a bulb check illumination and if they are self controlled or externally controlled.
ANALOGUE INSTRUMENTS
The analogue instruments are:
- speedometer
- tachometer
- fuel level gage
- engine coolant temperature gage.
Speedometer
The speedometer is an electrically driven, analogue instrument for displaying the vehicle speed. The pointer needle is electronically damped to prevent impacts on the vehicle wheels, causing deflection of the pointer needle.
The speedometer is driven by a CAN (controller area network) signal derived from the ABS (anti-lock brake system) module. The wheel speeds are measured by sensors reading rotational speed from toothed targets on the hubs. These speeds are passed to the ABS (anti-lock brake system) module in the form of pulsed signals. The ABS (anti-lock brake system) module is programmed that 48 pulses is equal to one revolution of the wheels and this equates in distance to approximately 2 meters.
This information is passed from the ABS (anti-lock brake system) module, on a high speed CAN (controller area network) signal, to the instrument cluster and is received by the microprocessor. The microprocessor applies a formula to the signal and calculates a numerical, 16 bit value for the signal. This signal is then used by the speedometer drive to display the current speed to the driver. A second digital signal output is also broadcast on the CAN (controller area network), I and K buses for use by other systems.
Two versions of the speedometer display are used. One shows the speed in kilometers per hour and the other shows the speed in miles per hour as the main display and kilometers per hour as a secondary display.
Tachometer
The tachometer is an electrically driven, analogue instrument for displaying the vehicle engine speed. The pointer needle is electronically damped to prevent impacts on the vehicle wheels, causing deflection of the pointer needle.
The tachometer is driven by an engine speed signal transmitted on the CAN (controller area network) from the ECM (engine control module).
Two versions of the tachometer are used for petrol and diesel engine variants. The petrol engine variants use a display which has a maximum engine speed reading of 7000 rev/min. The diesel engine variant uses a display which has a maximum engine speed reading of 6000 rev/min.
Fuel Level Gage
The fuel gage is an electrically driven, analogue instrument for displaying the fuel tank contents. The pointer needle is electronically damped to prevent impacts on the vehicle wheels, causing deflection of the pointer needle. When the ignition is off, the pointer returns to the empty position.
All fuel gage's, irrespective of market, use an imperial fraction reading marked 0 - 1 with graduations of 0, 1/4, 1/2, 3/4 and 1.
The instrument cluster is connected to two tank level sensors. One sensor is located in each side of the saddle type fuel tank and uses a float operated potentiometer for measuring the tank contents. Each tank level sensor is supplied with a current from the instrument cluster. The returned current, via the potentiometer of the sensor, is read by the processor. The reduced current from both sensors is evaluated and converted into a signal to position the fuel gage needle at the appropriate level reading.
When the processor determines that fuel tank contents have reached a predetermined level, the low fuel level warning indicator is illuminated and a chime is emitted from the sounder to alert the driver of the low fuel condition.
Engine Coolant Temperature Gage
The ECT (engine coolant temperature) gage is an electrically driven, analogue instrument for displaying the ECT (engine coolant temperature) to the driver. The pointer needle is electronically damped to prevent impacts on the vehicle wheels causing deflection of the pointer needle.
The ECT (engine coolant temperature) gage is the same on all cluster variants. The gage display has a blue segment for low temperatures and a red segment for excessively high temperatures. For normal engine operating temperatures the gage needle pointer is positioned centrally in the gage display zone. When the ignition is off, the pointer returns to the cold position.
The instrument cluster receives the ECT (engine coolant temperature) signal from the ECT (engine coolant temperature) sensor on a CAN (controller area network) signal from the ECM (engine control module).
The following table shows ECT (engine coolant temperature) relationship to gage needle pointer position.
SERVICE INTERVAL INDICATOR
The Service Interval Indicator (SII) is displayed as a message in the message center. The instrument cluster calculates the remaining distance to the next service and the remaining time to the next service.
BUS SYSTEMS
The instrument cluster has a controlling processor which processes software information and control input and output data for the instrument cluster and other systems. The processor communicates with other systems on the vehicle via a number of different interfaces.
Inputs are received as either analogue signals via conventional hardwired connections or as digital signals via multichannel connections with the bus systems. These signals are filtered and evaluated by the processor and the data converted into actuation of the analogue gages and warning indicator lamps.
The instrument cluster also functions as a gateway for the bus systems, processing data from one system protocol and translating it into another system protocol.
The instrument cluster receives and transmits data on the following bus systems:
NOTE: The instrument cluster provides a 'loop-through' for the high speed CAN (controller area network) bus.
REDUNDANT DATA STORAGE
CAUTION: When a new instrument cluster is to be installed, the Land Rover approved diagnostic system must be connected to vehicle and the instrument cluster renewal procedure followed to replace the cluster. This will ensure that vehicle coding data is correctly installed in the new instrument cluster. The Land Rover approved diagnostic system will also record the current service interval data and restore the settings to the new instrument cluster.
In the event of a new instrument cluster having to be installed, certain information needs to be maintained to prevent data loss. This information is transferred continuously from the instrument cluster on the I bus and is received and held in an EPROM (erasable programmable read only memory) in the LCM (lighting control module). The data is also stored, along with other vehicle specification data, in the ECM (engine control module).
The data stored is as follows:
- VIN (vehicle identification number)
- Total distance traveled
- Service interval fuel volume and type of last service
- Service interval clock.
When a new instrument cluster is installed, the LCM (lighting control module) will update the instrument cluster EPROM (erasable programmable read only memory) with the stored data providing the following parameters are met:
- The VIN (vehicle identification number) in the instrument cluster and the LCM (lighting control module) match
- The total distance reading in the instrument cluster EPROM (erasable programmable read only memory) is less than 158 miles (255 km)
- The total distance reading in the LCM (lighting control module) EPROM (erasable programmable read only memory) is less than 999,900 miles or kilometers or equal to or greater than 0 miles or kilometers
- The total distance recorded in the instrument cluster EPROM (erasable programmable read only memory) is less than the distance traveled stored in the LCM (lighting control module) EPROM (erasable programmable read only memory).
Vehicle coding data, such as engine type, market, etc., is stored in the ECM (engine control module) and retrieved by the Land Rover approved diagnostic system and used to update the new instrument cluster.
If the VIN (vehicle identification number) in the instrument cluster is set to 0, only service interval data is passed from the LCM (lighting control module) EPROM (erasable programmable read only memory) to the instrument cluster RAM (random access memory), it is not stored in the instrument cluster EPROM (erasable programmable read only memory). The total distance displayed in the odometer LCD (liquid crystal display) is frozen at the value stored in the instrument cluster EPROM (erasable programmable read only memory).
If any of the stored data in the LCM (lighting control module) EPROM (erasable programmable read only memory) conflicts with the data within the instrument cluster, a lamp, known as a manipulation point, is illuminated in the cluster. The manipulation point is located adjacent to the trip meter LCD (liquid crystal display).
The following conflicts will illuminate the manipulation point:
- The VIN (vehicle identification number) transferred from the LCM (lighting control module) on the I Bus to instrument cluster is 0
- The VIN (vehicle identification number) in the instrument cluster is 0
- The VIN (vehicle identification number) in the LCM (lighting control module) is different to the VIN (vehicle identification number) in the instrument cluster
- A default value in the EPROM (erasable programmable read only memory) is used until a CAN (controller area network) bus index message is sent when the ignition is switched on.
If the EPROM (erasable programmable read only memory) is in an unlocked (unprotected) condition, the manipulation point will flash, irrespective of whether or not the stored data matches or conflicts.
DIAGNOSTICS
The instrument cluster provides an interface (gateway) for data transfer between the Land Rover approved diagnostic system and the vehicle control modules. Individual control modules subject their functional capabilities to self diagnostic checks. Any irregularities or malfunctions are stored in the form of a DTC (diagnostic trouble code) in the control module error memory. The error memory can be interrogated by the Land Rover approved diagnostic system to establish and diagnose the cause of the DTC (diagnostic trouble code).
The instrument cluster RAM (random access memory) can be reset with the Land Rover approved diagnostic system. When this procedure is performed, all values stored in the RAM (random access memory) will be erased. Displayed values to the driver, such as trip meter reading and on-board computer sequence and values, will also be erased and resume their default values or are reset to values of zero.
The instrument cluster also performs a self diagnostic routine to check its function and monitoring of related components. Detected errors are written to the RAM (random access memory) initially and then transferred to the EPROM (erasable programmable read only memory) when the ignition is switched off. The EPROM (erasable programmable read only memory) will only store the five most recent errors (DTC (diagnostic trouble code) ). If five DTC (diagnostic trouble code) 's are stored, only further DTC (diagnostic trouble code) 's of the bus systems or instrument cluster EPROM (erasable programmable read only memory) DTC (diagnostic trouble code) 's will be memorized in their order of occurrence. DTC (diagnostic trouble code) 's already present will be over written. The DTC (diagnostic trouble code) 's can be retrieved and diagnosed with the Land Rover approved diagnostic system. When the instrument cluster is reset, DTC (diagnostic trouble code) 's stored in the EPROM (erasable programmable read only memory) are transferred to the RAM (random access memory) and then erased.