Range Rover P38
19
FUEL SYSTEM
NEW RANGE ROVER
6
DESCRIPTION AND OPERATION
Intake air temperature sensor (IAT sensor) -
Vehicles without EGR
Intake air temperature is monitored by a IAT sensor in
the intake manifold. The IAT sensor is of the NTC type
and is similar in operation to the fuel temperature
sensor previously described.
The ECM uses the information received from the IAT
sensor, in conjunction with the manifold absolute
pressure sensor, to determine the volume of air being
be drawn in to the engine.
1. Intake manifold
2. IAT sensor
EGR Modulator valve - Vehicles with EGR
The EGR modulator valve is located in the engine
compartment on the left inner wing near the bulkhead.
The EGR modulator valve is used to control the EGR
valve and is controlled by the ECM.
See EMISSION
CONTROL, Description and operation.
Manifold absolute pressure sensor (MAP sensor)
Inlet air pressure is monitored by a silicon diaphragm
type sensor mounted on top of the fuel filter and
connected, via a pressure tube to the intake manifold.
The MAP sensor is connected electrically to the ECM.
When inlet air pressure changes, pressure in the
detection chamber causes the diaphragms to deflect.
This alters the length of each resistor, changing their
resistance value. The change is detected by
electronics within the MAP sensor which varies the
output voltage. This is converted to a pressure
reading in the ECM.
Manifold absolute pressure, when linked to inlet air
temperature, gives an accurate measurement of the
charge volume. The ECM adjusts fuelling as
necessary.
Mass air flow sensor (MAF sensor) - Vehicles with
EGR
The MAF sensor is located in the air inlet pipe from
the air cleaner and is connected electrically to the
ECM. The sensor replaces the Air Intake Temperature
(IAT) sensor previously used on Pre-EGR vehicles.
The MAF sensor comprises a hot film sensor which
has a heated surface maintained by an electrical
current at a constant temperature. With cool air
flowing past the sensor, the volume of air drawn into
the intake manifold is measured by the electrical
current required to keep the temperature of the hot
film sensor constant.
The MAF sensor records the amount of incoming air
being drawn into the engine. The ECM uses this
information to control the Exhaust Gas Recirculation
(EGR) process.
See EMISSION CONTROL,
Description and operation.
