2002 LAND ROVER DISCOVERY turbo

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-11
Ambient Air Temperature and Pressure (AAP) sensor
The AAP sensor is located in the top of the air filter housing. It provides voltage signals relative to both ambient air
pressure and temperature to the ECM. The AAP sensor produces a voltage between 0 and 5 volts proportional to the
pressure level of the air in the air filter housing. A reading of 0 volts indicates low pressure and a reading of 5 volts
indicates high pressure. The ECM uses the signal from the AAP sensor for the following functions:
lTo maintain manifold boost pressure.
lTo reduce exhaust smoke emissions while driving at high altitude.
lControl of the EGR system.
The sensor also supplies a voltage between 0v and 5v proportional to ambient temperature. The ECM uses this signal
for the following functions:
lExhaust gas over temperature protection.
lTurbocharger overspeed protection.
Input/Output
Connector C0158 pin 8 of the ECM supplies the AAP sensor with a 5 volt power supply. The pressure output from the
AAP sensor is measured at pin 10 of the ECM connector C0158, the temperature output from the AAP sensor is
measured at pin 31. The earth path is via pin 30 of ECM connector C0158.
The AAP sensor can fail the following ways or supply incorrect signal:
lSensor open circuit.
lShort circuit to vehicle supply.
lShort circuit to vehicle earth.
lContaminated sensor element.
lDamaged sensor element.
lResistance in wiring harness.
In the event of an AAP sensor signal failure any of the following symptoms may be observed:
lAltitude compensation inoperative (engine will produce black smoke).
lActive boost control inoperative.
lTurbocharger boost pressure limited to 1 bar (14.5 lbf.in
2).
lEGR altitude compensation inoperative.
The MIL will not illuminate in an AAP sensor failure, and the ECM will use a fixed default value from its memory.

ENGINE MANAGEMENT SYSTEM - TD5
18-1-32 DESCRIPTION AND OPERATION
Turbocharger
1Exhaust gas from manifold
2Studs to exhaust manifold
3Turbocharger cast iron housing
4Wastegate valve linkage
5Exhaust gas out to front exhaust pipe
6Compressed intake air
7Fresh intake air
8Turbocharger aluminium alloy housing
9Wastegate valve vacuum port
The Td5 engine utilises a Garrett GT20 turbocharger with an electronically controlled wastegate modulator to improve
engine performance. The turbocharger uses the engine's exhaust gas to spin a turbine at very high speed. This
causes inlet air on the other side of the turbine to be drawn in through the turbocharger intake for compression. The
inlet air is carried round by the vanes of the compressor and then thrown out under centrifugal force from the
turbocharger's outlet duct. This compression of air enables a greater quantity of air to be delivered to the inlet manifold
via an intercooler. Combustion is improved through better volumetric efficiency. The use of a turbocharger improves
fuel consumption and increases engine torque and power. Exhaust noise is also reduced due to the smoothing out of
exhaust pulsations.
The rear cast iron body of the turbocharger housing connects to a port on the exhaust manifold at the LH side of the
cylinder head by three studs and nuts. The interface between the exhaust manifold and the turbocharger housing is
separated by a metal gasket. The exhaust outlet of the turbocharger is located at the bottom of the turbocharger cast
iron housing; it is connected to the exhaust system front downpipe and is attached by three studs and nuts. The
interface between the turbocharger housing and the exhaust front pipe is separated by a metal gasket.
The front casing of the turbocharger is constructed from aluminium alloy and is connected to the air inlet duct by a
metal band clip. The compressed air outlet is connected to the intercooler by a metal pipe which has rubber hose
extensions at each end attached by metal band clips.

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-33
The turbocharger is exposed to extremely high operating temperatures (up to 1,000 °C (1832 °F)) because of the hot
exhaust gases and the high speed revolution of the turbine (up to 150,000 rev/min). In order to resist wear of the
turbine bearings a flow of lubrication oil is supplied from the engine lubrication system to keep the bearings cool. Oil
is supplied from a tapping at the front of the full-flow filter adaptor housing via a metal pipe with banjo connections.
Oil is returned to the sump via a metal pipe which connects to the cylinder block at a port below the turbocharger
assembly.
A heatshield is attached to the left hand side of the engine to protect adjacent components from the heat generated
at the turbocharger. The heatshield is attached to the engine by two bolts an additional bolt attaches the heatshield
to the turbocharger casting.
The engine control module controls the amount of boost pressure the engine receives by way of the turbocharger.
When full boost is reached a control signal is sent to the wastegate modulator, and a vacuum is applied to the
wastegate valve. The wastegate valve opens, bypassing some of the exhaust gas away from the turbine to be output
to the exhaust system.
The engine should be allowed to idle for 15 seconds following engine start up and before the engine is switched off
to protect the turbocharger by maintaining oil supply to the turbine bearings.
Intercooler
The intercooler is an air-to-air heat exchanger which lowers the intake air temperature to obtain a higher air density
for better combustion efficiency. The intercooler receives compressed air from the turbocharger via a metal pipe; it
cools the intake air via the intercooler matrix and delivers it to the intake manifold by means of a rubber hose which
connects between the intercooler outlet and the intake manifold outlet. The rubber hose is connected to ports at each
end by metal band clips.

+ COOLING SYSTEM - Td5, DESCRIPTION AND OPERATION, Description.
The intercooler is located at the front of the engine bay, forward of the radiator.

ENGINE MANAGEMENT SYSTEM - TD5
18-1-34 DESCRIPTION AND OPERATION
Turbocharger wastegate modulator
The turbocharger wastegate modulator is located on the ancillary bracket on the engine, and is connected by flexible
pipes to the turbocharger. The modulator controls turbocharger boost pressure by varying the pressure used to open
the turbocharger wastegate. This control is vital to ensure the turbocharger does not over boost the engine.
Input/Output
The turbocharger wastegate modulator receives battery voltage from the main relay. The ECM supplies the earth path
in the form of a pulse width modulated (PWM) signal. The PWM signal from the ECM operates the modulator at a
frequency of less than 50 Hz. This signal allows the turbocharger wastegate modulator to open and close the
wastegate. This permits a proportion of the exhaust gas to bypass the turbocharger through the wastegate, thereby
regulating boost pressure.
Input voltage to the turbocharger wastegate modulator is via the main relay.
The earth path is via a PWM signal generated at pin 21 of the ECM connector C0158.
The turbocharger wastegate modulator can fail as follows:
lOpen circuit.
lShort circuit to voltage supply.
lShort circuit to vehicle earth.
lWiring loom fault.
lConnector water ingress.
lConnector failure due to excess heat.
lComponent failure due to excess heat.
lComponent failure due to excess vibration.
In the event of a turbocharger wastegate modulator failure any of the following symptoms may be observed:
lReduced engine performance.
lIncreased engine performance.
lLack of power.
lExcess smoke.
lReduced fuel economy.
The MIL will not illuminate in the event of a turbocharger wastegate modulator failure.

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-39
With the ECM in a 'Secure' state, it will not function unless an alarm system is fitted to the vehicle. A 'Secure' ECM
cannot be configured into a 'No Code' ECM.
With the ECM in a 'No Code' state, it does not require an alarm system to be fitted to allow the engine to operate. If
the ECM senses that an alarm system is fitted it will not start. A 'No Code' ECM can be configured to a 'Secure' ECM
using TestBook. A 'Secure' ECM can not be configured to a 'No Code' state.
Setting up of the ECM immobilisation configurations can only be performed using TestBook.
If a vehicle stalls immediately after starting it is possible that it has been immobilised. This means either:
lThe ECM was configured as 'No Code' but the ECM is receiving a code at its alarm input pin.
lThe ECM received an incorrect code.
lThe ECM was expecting a security code but did not receive one at its alarm input pin.
Fuel delivery/injection control
The fuel delivery/injection control delivers a precise amount of finely atomised fuel to mix with the air in the
combustion chamber to create a controlled explosion.
To precisely control fuel delivery and control fuel injection, the following input conditions must be met:
lCKP information.
lInjection timing map information.
lFT information.
lECT information.
The ECM monitors the conditions required for optimum combustion of fuel in the cylinder from the various sensors
around the engine and then compares it against stored information. From this calculation the ECM can adjust the
quantity and timing of the fuel being delivered to the cylinder.
The ECM uses CKP information as follows:
lTo calculate engine speed.
lTo determine engine crankshaft position.
Engine speed and crankshaft position allows the ECM to determine fuel injection timing.
The ECM also uses ECT information and FT sensor information to allow optimum fuel delivery and injection control
for all engine coolant and fuel temperatures.
Turbocharger control
Turbocharger control is vital to ensure the turbocharger does not over boost the engine. Within the turbocharger is a
wastegate, which when operated by the turbocharger wastegate modulator will open and close a bypass valve
regulating boost pressure.
The turbocharger wastegate modulator, via the ECM, controls boost pressure under the following conditions:
lAcceleration.
lWide open throttle.
lIdle.
lOverrun.
The turbocharger wastegate modulator receives a battery voltage supply from the main relay. The ECM supplies the
earth path in the form of a pulse width modulation (PWM) signal. This signal allows the turbocharger wastegate
modulator to open and close the wastegate. A proportion of the exhaust gas can bypass the turbocharger through
the wastegate, regulating boost pressure.

ENGINE MANAGEMENT SYSTEM - TD5
REPAIRS 18-1-55
Turbocharger
$% 19.42.01
Remove
1.Remove 3 bolts and remove engine acoustic
cover.
2.Release fixings and remove battery cover.
3.Disconnect battery earth lead.
4.Remove cooling fan cover.
5.Remove 3 bolts and remove exhaust manifold
heat shield.
6.Release clip and disconnect breather hose
from camshaft cover.
7.Release clip and disconnect vacuum hose from
turbocharger wastegate.
8.Loosen clips and release air intake and outlet
hoses from turbocharger. 9.Remove turbocharger oil feed banjo bolt and
discard sealing washers.
10.Remove 2 bolts and release turbocharger oil
drain pipe and discard gasket.
11.Remove 3 nuts and release exhaust front pipe
from turbocharger and discard gasket.
12.Remove 3 nuts securing turbocharger to
exhaust manifold.
13. Remove turbocharger and discard gasket.
Refit
1.Clean turbocharger and exhaust manifold
mating faces.
2.Using a new gasket, fit turbocharger to exhaust
manifold and tighten nuts to 30 Nm (22 lbf.ft).
3.Using new gasket, align exhaust front pipe and
tighten nuts to 30 Nm (22 lbf.ft).
4.Using new gasket, align turbocharger drain
pipe and tighten bolts to 9 Nm (7 lbf.ft).
5.Fit banjo bolt to oil feed pipe using new sealing
washers and tighten to 25 Nm (18 lbf.ft)..
6.Position air hoses to turbocharger and tighten
clips.
7.Position and secure breather hose to camshaft
cover.
8.Position and secure vacuum hose to
turbocharger wastegate.
9.Position exhaust manifold heat shield and
tighten M6 bolts to 9 Nm (7 lbf.ft) and M8 bolt to
25 Nm (18 lbf.ft).
10.Fit fan cowl and secure fixings.
11.Fit acoustic cover and secure the fixings.
12.Connect battery earth lead.
13.Fit battery cover and secure fixings.

MANIFOLDS AND EXHAUST SYSTEMS - TD5
30-1-2 DESCRIPTION AND OPERATION
Exhaust system component layout
1Tail pipe/silencer assembly
2Mounting rubber 4 off
3Turbo/Exhaust manifold gasket
4Flanged nut 3 off
5Front pipe assembly
6Flanged nut 2 off
7Intermediate pipe/silencer assembly
8Flanged nut 3 off
9Gasket

MANIFOLDS AND EXHAUST SYSTEMS - TD5
DESCRIPTION AND OPERATION 30-1-3
Description
General
The diesel engine has the inlet manifold attached to the right hand side of the engine and the exhaust manifold
attached to the left hand side of the engine. The inlet manifold directs cooled compressed air from the turbocharger
and intercooler into the cylinders, where it is mixed with fuel from the injectors. Exhaust gases from the exhaust
manifold can also be directed into the inlet manifold via a pipe from the exhaust manifold and an Exhaust Gas
Recirculation (EGR) valve on the inlet manifold. The exhaust manifold allows combustion gases from the cylinders to
leave the engine where they are directed into the exhaust system and turbocharger.
The exhaust system is attached to the turbocharger and is directed along the underside of the vehicle to emit exhaust
gases from a tail pipe at the rear of the vehicle. A silencer is installed midway along the system and a second tail
silencer is located at the rear of the vehicle.
Inlet manifold
The inlet manifold is a one piece aluminium casting. The manifold is secured to the cylinder head with two studs and
flanged nuts and eight flanged bolts. A one piece laminated gasket seals the manifold to the cylinder head.
Four threaded bosses on the manifold provide for the attachment of the fuel cooler. The fuel cooler is secured to the
manifold with four bolts. A boss with two threaded holes allows for the attachment of the combined intake air
temperature/pressure sensor. The sensor is secured to the manifold with two screws and sealed with a gasket.
At the forward end of the manifold, a machined face and four threaded holes provide for the attachment of the EGR
valve. The valve is sealed to the manifold with a gasket.

+ EMISSION CONTROL - Td5, DESCRIPTION AND OPERATION, Emission Control Systems.
Exhaust manifold
The exhaust manifold is made from cast iron. The manifold has five ports, one from each cylinder, which merge into
one flanged outlet connection positioned centrally on the manifold.
The manifold is attached to the cylinder head with ten studs and flanged nuts. A laminated metal gasket seals the
manifold to the cylinder head. The flanged outlet on the manifold provides the attachment for the turbocharger, which
is attached with three studs and flanged nuts and sealed with a metal laminated gasket.
A second flanged outlet, located at the forward end of the manifold, provides attachment for the EGR pipe. The EGR
pipe is secured to the manifold with two cap screws and connected to the EGR valve mounted on the inlet manifold.
There is no gasket used between the pipe and the exhaust manifold.

+ EMISSION CONTROL - Td5, DESCRIPTION AND OPERATION, Emission Control Systems.
Exhaust system
The exhaust system comprises a front pipe, an intermediate pipe which incorporates a silencer and a tail pipe
assembly which also has a silencer. The exhaust system is constructed mainly of 63 mm (2.48 in) diameter extruded
pipe with a 1.5 mm (0.06 in) wall thickness. All pipes are aluminized to resist corrosion and the silencers are fabricated
from stainless steel sheet.