The Garage 285

31 focus Engine Management
bad
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not easy and few repairers
have their own in-house
provision. Instead, many
independent repairers have
no choice but to replace the
system outright, or pass the
work over to dealers.
“This is an expensive solution
for both repairers and
the end customer, especially
when the system is still repairable.
What’s more, due
to repair costs, and the
significant profit that can
be made from installing a
new ECU, the majority of
franchised dealers opt to
replace, rather than repair,
which is not the best result
for the customer.”
Current engines feature
camshaft and crankshaft
sensors, and come in inductive
or hall effect forms. In
the former a magnet and coil
detect teeth on the shaft’s
gearwheel and thus creating
a voltage change which produces
a waveform output
signal. Hall effect types create
a digital sensor.
According to Elta oil contamination
or damage to
connectors can cause fault
codes but, when it comes to
replacement, there are some
basic steps to ensure the
task is carried out properly.
“The correct positioning
of the new sensor is critical
as camshaft sensors often
feature slotted mounting
holes and/or locating pins.
Therefore, ensure that any
locating pins are correctly
seated before fully slotting
into place. Failure to do so
can shear off the locating
pin, causing misalignment
of the sensor and incorrect
readings. Finally, reconnect
wiring and reset the ECU if
needed,” Elta says.
Some sensors are far more
difficult to replace but when
it comes to warranty returns,
the sensor is often not
the cause of its return
“Some cam/crankshaft
sensors are particularly difficult
to replace, usually
due to awkward fitting locations
or angles within the
engine bay, camshaft sensor
EE0018 being a perfect example.
This sensor has the
highest return rate under
warranty, but when tested
the diagnosis usually rejects
the claim as it is not faulty,
but damaged due to a fitting
error.
“This is down to the fact
that this sensor is located in
a particularly tricky position
and is often returned with
the locating lug sheared off,
probably as a result of securing
the sensor into place
without correct alignment.
The slight misalignment of
the sensor has a dramatic
effect on its performance.”
Much of the emphasis on
greater economy and performance,
as well as reduced
emissions focuses on the
air/fuel mix, especially by the
time it reaches the catalytic
convertor, which is where
the lambda sensor steps in.
According to Hella faulty
lambda sensors can cause
a multitude of problems
including increased fuel
consumption, sluggish performance
and increased
emissions, with faults
caused by short circuiting,
overheating or the use of fuel
additives.
“The lambda sensor principle
is based on an oxygen
comparison measurement.
This means that the remaining
oxygen content of the exhaust
emission (approx. 0.3
– three percent) is compared
with the oxygen content of
the ambient air (approx.
20.8 percent),” Hella says.
“The function of the lambda
sensor is usually checked
during the routine exhaust
emissions test. However,
since it is subject to a certain
amount of wear, it should
be checked at regular intervals
(approx. every 20,000
miles), to ensure that it is
working properly.”
Replacement should be
handled carefully and, says
Hella, using specific tools and
keeping the sensor’s probe
measurement away fro oil,
water and grease: damaged
sensors and those that have
been dropped should not be
used, Hella counsels.
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