2002 LAND ROVER DISCOVERY Fuel system

ENGINE MANAGEMENT SYSTEM - TD5
18-1-6 DESCRIPTION AND OPERATION
Description
General
An engine control module (ECM) controls the five-cylinder direct injection diesel engine, and works on the drive by
wire principle. This means there is no throttle cable, the ECM controls the drivers needs via a signal from the Throttle
Position (TP) sensor on the throttle pedal.
The ECM is a full authoritative diesel specific microprocessor that also incorporates features for cruise control and air
conditioning control. In addition, the ECM supplies output control for the exhaust gas recirculation and turbocharger
boost pressure. The ECM has a self-diagnostic function, which is able to provide backup strategies for most sensor
failures.
The ECM processes information from the following input sources:
lMass air flow sensor.
lAmbient air pressure sensor.
lManifold absolute pressure/inlet air temperature sensor.
lEngine coolant temperature sensor.
lCrankshaft speed and position sensor.
lThrottle position sensor.
lFuel temperature sensor.
lAir conditioning request.
lAir conditioning fan request.
lBrake pedal switch.
lClutch switch.
lCruise control master switch.
lCruise control SET+ switch.
lCruise control RES switch.
lHigh/low ratio switch.
The input from the sensors constantly updates the ECM with the current operating condition of the engine. Once the
ECM has compared current information with stored information within its memory, it can make any adjustment it
requires to the operation of the engine via the following:
lAir conditioning clutch relay.
lAir conditioning cooling fan relay.
lElectronic vacuum regulator solenoid.
lMalfunction indicator lamp.
lFuel pump relay.
lGlow plug warning lamp.
lGlow plugs.
lFuel injectors.
lMain relay.
lTurbocharger wastegate modulator.
lTemperature gauge.
The ECM interfaces with the following:
lElectronic Automatic Transmission (EAT).
lSelf Levelling and Anti-lock Brakes System (SLABS).
lSerial communication link.
lInstrument cluster.
lBody Control Unit (BCU).

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-9
Connector C0658
Pin No. Input/Output Function Signal type Value Interfaces
B1 Input Earth 1 0 volts 0 volts
B2 Input Earth 4 0 volts 0 volts
B3 Input Supply battery voltage 12 volts 12 volts
B4 Output Cooling fan relay Switch 12-0 volts A/C ECU
B5 Output Fuel pump relay Switch 12-0 volts
B6 Output MIL Switch 12-0 volts Instruments
B7 Output Temperature gauge Digital 0-12 volts Instruments
B8 Not used
B9 Input A/C clutch request Switch 12-0 volts A/C ECU
B10 Input Normally closed brake
switchSwitch 12-0 volts
B11 Input Cruise control SET+ switch Switch 12-0 volts
B12 Input TP sensor 1 Analogue 0- 5 volts
B13 Input Vehicle speed Digital 0-12 volts
B14 Input TP sensor supply 5 volts 5 volts
B15 Input Cruise control master switch Switch 12-0 volts
B16 Input Normally open brake switch Switch 0-12 volts
B17 Input Cruise control RES switch Switch 12-0 volts
B18 Input/Output Serial communication link Digital 0-12 volts All ECU's
B19 Output Tachometer engine speed Digital 0-12 volts Instrument
Cluster
B20 Not used
B21 Output Main relay Switch 0-12 volts
B22 Input Supply battery voltage 12 volts 12 volts
B23 Input A/C fan request Switch 12-0 volts
B24 Input Earth 3 0 volts 0 volt
B25 Input Earth 2 0 volts 0 volts
B26 Input TP sensor earth 0 volts 0 volts
B27 Input Supply 2 12 volts 12 volts
B28 Not used
B29 Output A/C relay Switch 12-0 volts
B30 Output Glow plug warning light Switch 12-0 volts Instrument
Cluster
B31 Not used
B32 Output ABS digital 0-5 volts SLABS
B33 Input Ignition Switch 0-12 volts
B34 Input Security code digital 0-5 volts
B35 Input Clutch switch Switch 12-0 volts
B36 Input TP sensor 2 Analogue 5-0 volts

ENGINE MANAGEMENT SYSTEM - TD5
18-1-12 DESCRIPTION AND OPERATION
Manifold Absolute Pressure (MAP)/Inlet Air Temperature (IAT) sensor
The MAP/IAT sensors are combined in one unit located in the inlet manifold. It provides pressure and temperature
information about the air in the inlet manifold to the ECM. The ECM compares the voltage signal to stored values and
compensates fuel delivery as necessary. The ECM uses the signal from the MAP/IAT sensor for the following
functions:
lTo calculate the delivered fuel limits.
lTo calculate the air mass in the cylinder.
lTo calculate the air speed density.
lTo calculate air temperature.
The MAP sensor works on the piezo crystal principal. Piezo crystals are pressure sensitive and will oscillate in
accordance to changes in air pressure. The MAP sensor produces a voltage between 0 and 5 volts proportional to
the pressure level of the air in the inlet manifold. A reading of 0 volts indicates a low pressure and a reading of 5 volts
indicates a high pressure.
The IAT portion of the sensor works as a Negative Temperature Co-efficient (NTC) sensor. As air temperature rises,
the resistance in the sensor decreases. As temperature decreases the resistance in the sensor increases. The ECM
compares the voltage signal to stored values and compensates fuel delivery as necessary.
Input/Output
The ECM provides the MAP/IAT sensor with a 5 volt supply. There are 2 output signals from the sensor, one from the
MAP and one from the IAT. Input to the MAP/IAT comes from pin 8 of the ECM connector C0158. Output from the
MAP is measured at pin 6 of the ECM connector C0158. IAT output signal measured at pin 34 of the ECM connector
C0158. The earth path is via pin 17 of ECM connector C0658. The MAP/IAT sensors share the same common earth.

ENGINE MANAGEMENT SYSTEM - TD5
18-1-14 DESCRIPTION AND OPERATION
Engine Coolant Temperature (ECT) sensor
The ECT sensor is located in the coolant outlet elbow on the top of the engine. It provides the ECM with engine coolant
temperature information. The ECM uses this ECT information for the following functions:
lFuelling calculations.
lTemperature gauge.
lTo limit engine operation if coolant temperature is too high.
lCooling fan operation.
lGlow plug operating time.
The ECT works as an NTC sensor. As temperature rises, the resistance in the sensor decreases, as temperature
decreases, the resistance in the sensor increases. The ECM compares the voltage signal to stored values and
compensates fuel delivery to ensure optimum driveability at all times.
Input/Output
The inputs and outputs for the ECT are earth and signal out.
The ECT signal is measured at pin 7 of the ECM connector C0158. The earth path is via pin 18 of ECM connector
C0158.
ECT sensor temperature to resistance table.
Temperature, °C Temperature, °F Resistance, ohms
nominal)
-10 14 9397
0325896
10 50 3792
30 86 1707
50 122 834.0
70 158 435.7
90 194 243.2
110 230 144.2
130 266 89.3

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-15
The ECT sensor can fail the following ways or supply incorrect signal:
lSensor open circuit.
lShort circuit to vehicle supply.
lShort circuit to earth.
lIncorrect mechanical fitting.
lSignal fixed above 40
°C (104 °F) not detected.
lSignal fixed below 40
°C (104 °F) not detected.
In the event of an ECT sensor signal failure any of the following symptoms may be observed:
lDifficult cold start.
lDifficult hot start.
lDriveability concerns.
lInstrument pack temperature warning illuminated.
lTemperature gauge reads excessively hot.
lTemperature gauge reads excessively cold.
In the event of component failure the ECM calculates coolant temperature from the fuel temperature sensor signal. If
this occurs, the limit engine operation if coolant temperature is too high becomes inoperative.
The MIL will not illuminate in an ECT sensor failure.

ENGINE MANAGEMENT SYSTEM - TD5
18-1-16 DESCRIPTION AND OPERATION
Crankshaft speed and Position (CKP) sensor
The CKP is located in the transmission housing with its tip adjacent to the outer circumference of the flywheel. The
CKP sensor works on the variable reluctance principle, which sends a signal back to the ECM in the form of an ac
voltage.
The ECM uses the signal from the CKP for the following functions:
lTo calculate engine speed.
lTo determine engine crank position.
lTo determine fuel injection timing.
The CKP sensor works as a Variable Reluctance Sensor (VRS). It uses an electromagnet and a target ring to generate
a signal. As the target ring passes the tip of the CKP sensor the magnetic field produced by the sensor is cut and then
re-instated. The ECM measures the signal as an ac voltage.
The outer circumference of the flywheel acts as the target ring for the sensor. The flywheel is divided into 36 segments
each of 10
°. 31 segments have drilled holes and 5 segments are spaces. This equals 360° or one engine revolution.
The 5 spaces correspond to the TDC position of the 5 cylinders, this allows the ECM to control fuel injection timing
for each of the cylinders.
Input/Output
The two pins on the sensor are both outputs. The ECM processes the outputs of the sensor. To protect the integrity
of the CKP signal an earth shield or screen is used.
The ECM measures the outputs from the CKP. The ECM measures the positive signal from the CKP at pin 13 of ECM
connector C0158. The ECM measures the negative signal from the CKP at pin 36 of ECM connector C0158. The earth
path is via pin 16 of ECM connector C0158.
Voltage generation from the CKP sensor is relative to engine speed. The values expected from a good CKP sensor
are as follows:
l2 to 3 volts with engine cranking.
lRising to 6 to 6.5 volts from 1000 rev/min upwards.
The above readings are dependent upon correct air gap between the tip of the CKP sensor and the passing teeth of
the reluctor ring.

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-19
Throttle Position (TP) sensor – From VIN 297137
Discovery Series II vehicles from VIN 297137 use three track thick film potentiometers. No idle speed sender switch
is used on this type of sensor because the ECM can compare the two or three sets of signals to implement idle speed
control and over-run fuel shut-off. The two potentiometers are known as track 1 and 2 potentiometers. The track 3
potentiometer on later models is used to improve the resolution of the pedal. The ECM provides a 5V supply and
receives a signal from each of the potentiometer tracks.
a = Track 1
b = Track 2
c = Track 3
d = Voltage
e = Pedal angle (degrees)
f = Wide open throttle stop tolerance band
g = Not applicable for Discovery Series II.
With reference to the above graph, at idle (throttle released), track 2 returns a signal of 4.2V to the ECM and track 1
returns a signal of 0.8V. The ECM calculates the sum of these two figures which totals 5.0V.
At wide open throttle, track 2 returns a signal of 1.1V and track 1 returns a signal of 3.9V to the ECM. The ECM
calculates the sum of these two figures which totals 5.0V. The ECM uses this strategy to error check the TP sensor
signal and ensure that the requested throttle position is applied. The third potentiometer track measures the tolerance
of tracks 1 and 2 and provides an improved functionality check of the pedal angle.
NOTE: Three track TP sensors cannot be fitted as replacements on vehicles previously fitted with two track TP
sensors. Replacement ECM's are configured for two track TP sensors and can be fitted to all Td5 models. When
replacement ECM's are fitted to vehicles using three track TP sensors, TestBook or T4 must be used to configure the
ECM for three track TP sensor use.
If the TP sensor fails, the ECM will illuminate the MIL and the engine will operate at normal idle speed only.

ENGINE MANAGEMENT SYSTEM - TD5
18-1-20 DESCRIPTION AND OPERATION
Electronic Unit Injector (EUI)
The EUI's are located in the top of the engine inside the camshaft cover. There is one EUI per cylinder. They inject
finely atomised fuel directly into the combustion chamber. Each EUI has its own electrical connection, which is linked
to a common harness also located under the camshaft cover. Each of the EUI has its own 5 letter grading code. This
code is used so that greater EUI precision is achieved.
The ECM provides the earth path for the EUI. Using an injection-timing map within its memory and information from
the crankshaft speed and position sensor the ECM is able to determine precise crankshaft angle. When the ECM
determines the crankshaft speed and position it closes the spill valve within the EUI. Fuel pressure rises inside the
EUI to a predetermined limit of, 1500 bar (22,000 lbf.in
2) on pre EU3 models, and 1750 bar (25,500 lbf.in2) on EU3
models, at this limit the pintle lifts off its seat allowing the fuel to inject into the combustion chamber. The ECM de-
energises the spill valve to control the quantity of fuel delivered. This causes a rapid pressure drop within the EUI
which allows the EUI return spring to re-seat the pintle ending fuel delivery.
The electrical circuit that drives the EUI works in two stages depending on battery voltage. If battery voltage is
between 9 and 16 volts the EUI's will provide normal engine performance. If however battery voltage falls to between
6 and 9 volts, on pre EU3 models, EUI operation is restricted to a limit of 2100 rev/min, on EU3 models EUI operation
is restricted to idle.
If the vehicle is fitted with a new ECM, the EUI grades for that specific vehicle must be downloaded to the new ECM
using TestBook. In the event of the engine failing to rev above 3000 rev/min it is probable that the EUI grading has
not been completed.
Input/Output
Input to the EUI takes the form of both mechanical and electrical signals. The mechanical input to the EUI is diesel
fuel via the fuel pump operating at approximately 4 to 5 bar (58 to 72 lbf.in
2). Each of the EUI's is operated
mechanically by an overhead camshaft to enable injection pressures of up to 1500 bar (22,000 lbf.in2) on pre EU3
models, and 1750 bar (25,500 lbf.in2) on EU3 models, to be achieved. The ECM controls the EUI's to ensure that fuel
delivery is precise and as intended.