Range Rover P38
19
FUEL SYSTEM
NEW RANGE ROVER
46
DESCRIPTION AND OPERATION
A software strategy within the ECM enables the
closed throttle position to be learnt, so that the sensor
can be fitted without the need for adjustment.
The throttle position signal is also supplied to the EAT
ECU from the ECM using the CAN communication
link. The EAT ECU uses the throttle position data to
determine the correct point for gear shifts and
acceleration kickdown.
If the TP sensor signal fails, the ECM uses a default
value derived from engine load and speed. A TP
sensor failure may result in the following symptoms
being experienced:
•
Poor throttle response and degraded engine
performance
•
Emission control failure.
•
Closed loop idle speed control inoperative.
•
Automatic gearbox kickdown inoperative.
•
Incorrect altitude adaption
•
MIL illuminated (NAS only)
A TP sensor failure is likely to occur for the following
reasons:
•
Sensor open circuit
•
Short circuit of signal line to vehicle supply, 5V
supply or ground.
•
Bad connection or increased resistance in wiring
harness causing signal offset.
•
Blocked air filter (load monitoring, ratio of the TP
sensor to air flow).
•
Restricted air inlet (load monitoring, ratio of the
TP sensor to air flow).
If the TP sensor should fail, the following fault codes
will be generated by the ECM diagnostics, which can
be retrieved by Testbook:
•
P0101 - (load monitoring, the ratio of throttle
position to air flow).
•
P0122 - (signal less than the minimum
threshold).
•
P0123 - (signal greater than the maximum
threshold).
Engine Coolant Temperature (ECT) sensor - (from
99MY)
The ECT sensor is located at the top front of the
engine, adjacent to the coolant outlet pipe. The sensor
screws into a thread in the inlet manifold and
incorporates a sealing ring between the faces of the
sensor and manifold.
The ECT sensor multiplug has four wires; two are the
signal and ground connections used by the ECM, the
other two are used by the body control module
(BeCM) for control of the temperature warning lamp
operation on the instrument pack.
The sensor contains two thermistors with negative
temperature co-efficients; as temperature increases,
the thermistor’s resistance decreases. The ECM
receives a corresponding analogue input voltage
between 0 and 5V.
NOTE: The temperature / resistance
characteristics of the two thermistors
differ, and so it is important to maintain
the correct pin-outs.
The ECM uses the information received from the ECT
sensor to make adjustments to the engine operating
conditions. The ECM ensures a richer air:fuel mixture
is available at lower block temperatures for good
quality starts and smooth running. The mixture is then
made leaner as the engine temperature rises to
maintain low emissions and good performance.
For NAS vehicles with secondary air injection, the
signal from the ECT sensor is monitored at engine
start, to determine whether the conditions are cold
enough to warrant secondary air injection to be
employed. The ECT sensor is then monitored to
switch off the secondary air injection when the
required engine coolant temperature has been
attained.