1999 LAND ROVER DEFENDER sensor

18 - ENGINE MANAGEMENT SYSTEM
CONTENTS
Page
DESCRIPTION AND OPERATION
COMPONENT LOCATION 2...................................................................................
DESCRIPTION 5.....................................................................................................
ENGINE CONTROL MODULE (ECM) 6.................................................................
SENSOR - MASS AIR FLOW (MAF) 7....................................................................
SENSOR - AMBIENT AIR PRESSURE AND 8.......................................................
SENSOR - MANIFOLD ABSOLUTE PRESSURE 9................................................
SENSOR - ENGINE COOLANT TEMPERATURE 11.............................................
SENSOR - CRANKSHAFT SPEED AND 12...........................................................
SENSOR - THROTTLE POSITION (TP) 14............................................................
SENSOR - THROTTLE POSITION (TP) 15............................................................
ELECTRONIC UNIT INJECTOR (EUI) 18...............................................................
SENSOR - FUEL TEMPERATURE (FT) 20............................................................
RELAY - FUEL PUMP 21........................................................................................
RELAY - MAIN 21...................................................................................................
SWITCH - BRAKE PEDAL 22.................................................................................
SWITCH - CLUTCH PEDAL 22...............................................................................
MODULATOR - EXHAUST GAS REGULATOR (EGR) 23.....................................
WARNING LAMP - GLOW PLUG 23......................................................................
GLOW PLUGS 24...................................................................................................
TURBOCHARGER 26.............................................................................................
INTERCOOLER 27.................................................................................................
OPERATION 28......................................................................................................
REPAIR
ENGINE CONTROL MODULE (ECM) 1.................................................................
SENSOR - ENGINE COOLANT TEMPERATURE (ECT) 1....................................
SENSOR - CRANKSHAFT SPEED AND POSITION (CKP) 2................................
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ENGINE MANAGEMENT SYSTEM
3
DESCRIPTION AND OPERATION 1.Mass Air Flow (MAF) sensor.
2.Engine Coolant Temperature (ECT) sensor.
3.Glow plugs.
4.Manifold Absolute Pressure (MAP) / Inlet Air Temperature (IAT) sensor.
5.Fuel pump relay.
6.Engine Control Module (ECM).
7.Air Conditioning (A/C) and cooling fan relay.
8.Fuel Temperature (FT) sensor.
9.Crankshaft Speed and Position (CKP) sensor.
10.Electronic Unit Injectors (EUI).
11.Ambient Air Pressure (AAP) sensor.
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ENGINE MANAGEMENT SYSTEM
5
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 principal. 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 air conditioning. In
addition, the ECM supplies output control for the Exhaust Gas Recirculation (EGR) 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:
Mass Air Flow (MAF) sensor.
Ambient Air Pressure (AAP) sensor.
Manifold Absolute Pressure (MAP) / Inlet Air Temperature (IAT) sensor.
Engine Coolant Temperature (ECT) sensor.
Crankshaft Speed and Position (CKP) sensor.
Throttle Position (TP) sensor.
Fuel Temperature (FT) sensor.
Air conditioning request.
Air conditioning fan request.
Brake pedal switch.
Clutch pedal 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:
Air conditioning clutch relay.
Air conditioning cooling fan relay.
Electronic vacuum regulator solenoid.
Fuel pump relay.
Glow plug warning lamp.
Glow plugs.
Fuel injectors.
Main relay.
Turbocharger wastegate modulator.
Temperature gauge.
The ECM interfaces with the following:
Serial communication link.
Instrument pack.
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18ENGINE MANAGEMENT SYSTEM
6
DESCRIPTION AND OPERATION ENGINE CONTROL MODULE (ECM)
The ECM is made from aluminium alloy and is located under the RH front seat. The ECM has an interface of 72
pins via two connectors providing both input information and output control. The ECM receives information from
the sensors to inform it of the current state of the engine. The ECM then refers this information to stored values in
its memory and makes any changes to the operation of the engine necessary via the actuators. This is a rolling
process and is called adaptive strategy. By using this adaptive strategy the ECM is able to control the engine to
give optimum driveability throughout all operating conditions. There is no ECM self test, although the ECM saves
driveability data from the last journey. Power down of the ECM can take between 10 seconds and 10 minutes
dependent on coolant temperature.
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ENGINE MANAGEMENT SYSTEM
7
DESCRIPTION AND OPERATION SENSOR - MASS AIR FLOW (MAF)
The MAF sensor is located in the intake system between the air filter housing and the turbocharger. The ECM
uses the information generated by the MAF sensor to control exhaust gas recirculation (EGR).
The MAF sensor works on the hot film principal. The MAF sensor has 2 sensing elements contained within a film.
One element is controlled at ambient temperature e.g. 25°C (77°F) while the other is heated to 200°C (360°F)
above this temperature e.g. 225°C (437°F). As air passes through the MAF sensor the hot film will be cooled.
The current required to keep the constant 200°C (360°F) difference provides a precise although non-linear signal
of the air drawn into the engine. The MAF sensor sends a voltage of between 0 and 5 volts to the ECM,
proportional to the mass of the incoming air. This calculation allows the ECM to set the EGR ratio for varying
operating conditions.
Inputs / Outputs
The MAF sensor receives battery voltage (C0149-3) via the ECM on a brown/orange wire. Signal output on a
slate/light green wire from the MAF sensor (C0149-2) to the ECM (C0158-11) is a variable voltage proportional to
the air drawn into the engine. The MAF sensor is provided an earth (C0149-1) via the ECM (C0158-20) on a
pink/black wire.
The MAF sensor can fail or supply an incorrect signal if one or more of the following occurs:
Sensor open circuit.
Short circuit to vehicle supply.
Short circuit to vehicle earth.
Contaminated sensor element.
Damaged sensor element.
Damaged wiring harness.
MAF sensor supplies incorrect signal (due to air leak or air inlet restriction).
In the event of a MAF sensor signal failure any of the following symptoms my be observed:
During driving, engine speed may dip before recovering.
Difficult starting.
Engine stalls after starting.
Delayed throttle response.
EGR inoperative.
Reduced engine performance.
MAF signal out of parameters.
In the event of a MAF sensor failure, the ECM will use a fixed default value from its memory.
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18ENGINE MANAGEMENT SYSTEM
8
DESCRIPTION AND OPERATION SENSOR - AMBIENT AIR PRESSURE AND
TEMPERATURE (AAP)
The AAP sensor is located in the top of the air filter housing. It provides a voltage signal relative to ambient air
pressure to the ECM. The AAP sensor works on the piezo crystal principal. Piezo crystals are pressure sensitive
and will oscillate in accordance to changes in air pressure. 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 a high pressure. The ECM uses this signal for the following functions.
To maintain manifold boost pressure.
To reduce exhaust smoke emissions while driving at high altitudes.
Control of the EGR system.
Inputs / Outputs
The ECM (C0158-8) supplies the AAP sensor (C0188-3) with a 5 volt feed on a pink/purple wire. The output signal
from the AAP sensor (C0188-2) is sent to the ECM (C0158-10) on a white/yellow wire. The AAP sensor is earthed
(C0188-1) via the ECM (C0158-30) on a pink/black wire.
The AAP sensor can fail, or supply an incorrect signal if one or more of the following occurs:
Sensor open circuit.
Short circuit to vehicle supply.
Short circuit to vehicle earth.
Contaminated sensor element.
Damaged sensor element.
Resistance in wiring harness.
In the event of an AAP sensor signal failure, any of the following symptoms may be observed:
Altitude compensation inoperative (engine will produce black smoke).
Active boost control inoperative.
Turbocharger boost pressure limited to 1 bar (14.5 lbf.in
2).
EGR altitude compensation inoperative.
In the event of a AAP sensor failure, the ECM will use a fixed default value from its memory.
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ENGINE MANAGEMENT SYSTEM
9
DESCRIPTION AND OPERATION SENSOR - MANIFOLD ABSOLUTE PRESSURE
(MAP) / INLET AIR TEMPERATURE (IAT)
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:
To calculate the delivered fuel limits.
To calculate the air mass in the cylinder.
To calculate the air speed density.
To calculate the 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, a reading of 5 volts
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.
Inputs / Outputs
The MAP/IAT sensor (C0567-3) is provided a 5 volt supply by the ECM (C0158-8) on a pink/purple wire. The
MAP/IAT sensor provides the ECM with 2 outputs. The MAP sensor output (C0567-4) is connected to the ECM
(C0158-6) by a white/yellow wire. The IAT sensor output (C0567-2) is connected to the ECM (C0158-34) on a
green/black wire. The MAP/IAT sensor is earthed (C0567-1) via the ECM (C0158-17) on a pink/black wire.
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18ENGINE MANAGEMENT SYSTEM
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DESCRIPTION AND OPERATION The MAP/IAT sensor can fail, or supply an incorrect signal if one or more of the following occur:
Sensor open circuit.
Short circuit to vehicle supply.
Short circuit to vehicle earth.
Contaminated sensor element.
Damaged sensor element.
Resistance in wiring harness.
In the event of a MAP/IAT sensor failure any of the following symptoms may be observed:
If the MAP sensor fails manifold pressure is set to a pre-determined default value and the engine performance
will be reduced.
If the IAT sensor fails the ECM will set air temperature to a fixed value. The ECM will use a fixed default value
from its memory.
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