Range Rover P38
LAND ROVER V8
23
DESCRIPTION AND OPERATION
Knock Sensors (KS) - up to 99MY
The knock sensor produces an output voltage which is
proportional to mechanical vibration caused by the
engine. A sensor is located in each cylinder bank
between 2/4 and 3/5 cylinders. The ECM calculates if
the engine is knocking by taking camshaft and
crankshaft sensor signals to determine the position of
the engine in the combustion cycle.
The ECM can also work out exactly which cylinder is
knocking and progressively retards the ignition on that
particular cylinder until the knock disappears. It then
advances the ignition to find the optimum ignition
timing for that cylinder.
The ECM can simultaneously adjust the timing of
each cylinder for knock. It is possible that all eight
cylinders could have different advance angles at the
same time. If the camshaft sensor fails, the knock
control will be disabled.
Fault codes:
•
P0331 - Continuous knock on bank B
•
P0332 - Knock background noise low, bank B
•
P0333 - Knock background noise high, bank B
•
P0326 - Continuous knock on bank A
•
P0327 - Knock background noise low, bank A
•
P0328 - Knock background noise high, bank A
Ignition coils - up to 99MY
The electronic ignition system uses four double ended
coils. The ignition coils are mounted on a bracket
fitted to the rear of the engine. The circuit to each coil
is completed by switching within the ECM, allowing
each coil to charge. When the ECM determines the
correct ignition point, it switches off current supply to
the coil which in turn causes the magnetic field around
the coil’s primary winding to collapse, inducing ht
voltage in the secondary winding and in the iron core
of the coil. High tension voltage, of different polarities,
is produced at either end of the coil’s core and is
transmitted to two cylinders simultaneously, one on
compression stroke, the other on exhaust stroke. This
is called the wasted spark principle.
Note that coil 1 feeds cylinders 1 and 6, coil 2 feeds
cylinders 5 and 8, coil 3 feeds cylinders 4 and 7, and
coil 4 feeds cylinders 2 and 3. The resistance of the
spark plug in the compression cylinder is higher than
that in the exhaust cylinder and hence more spark
energy is dissipated in the compression cylinder. Coil
failure will result in a lack of ignition, resulting in a
misfire in the related cylinders. The fault is indicated
by illumination of the malfunction indicator light (MIL)
on North American specification vehicles.
