DIAGNOSTI C S
November/December 2018 | VehicleServicePros.com 47
Types of regeneration
Th ere are three types of DPF regeneration:
passive, active and forced. A passive regeneration
uses a diesel oxidation catalyst (DOC) alone
that acts to heat air before it reaches the fi lter. Th e
vehicle must be driven at a signifi cant speed for
a period of 30 to 50 minutes to allow the exhaust
temperature to rise high enough to adequately
burn the soot.
Some fl eets may never generate
enough heat automatically,
due to being driven locally with
a series of stops and starts. An
alternative type of regeneration
was devised called active
regeneration to handle these
situations. An active regeneration
injects extra fuel or
diesel exhaust fl uid to increase
the temperature high enough
to incinerate the trapped soot
within the fi lter.
Neither passive nor active
regenerations require the
vehicle operator to take active
measures. However, when
both previous processes fail
and a REGEN malfunction
light displays yellow on the
driver’s dashboard, it’s time to
take real action. Fleets should
not wait for the light to fl ash
red and risk damaging the
engine. It is important to note
that regeneration will not be
initiated if any engine codes
are detected. To this point,
it’s vital to address engine
and exhaust system failures
upstream from the DPF as
these failures may have a critical
eff ect on the DPF and the
frequency and success of any
type of DPF regeneration.
Th e third type of regeneration
is referred to as manual
regeneration, sometimes
called a forced regeneration.
Th is process must be completed
in the shop by a technician,
using a scan tool with manual
regen capabilities.
Just like other vehicle diagnostics
using a scan tool,
technicians must plug the
diagnostic tool into the vehicle’s
OBD port. Depending on
the scan tool used, condition of
the fi lter and the vehicle type,
a static forced regeneration
can take up to an hour. Some
vehicles require an in-motion
forced regeneration whereby
the vehicle would need to be
driven at specifi c a speed and
distance while the diagnostic
tool is connected to the OBD
port. An additional technician
should be present in the
vehicle while in operation to
observe displayed process and provide feedback
information from the diagnostic device.
A scan tool that can automatically scan all
systems and view live data can provide information
on how the engine is functioning, in addition
to the condition of the DPF. Some scan tools
may also have the ability to run a forced regeneration
when passive and active regenerations
have failed. When technicians are completing
this service on the vehicle, they should also
complete a thorough inspection of upstream
systems such as the injectors, exhaust system
and coolant system as well.
Th e DPF system is just one of the many
systems so vital to optimum vehicle operation.
Giving it proper attention and care is equally
as vital to ensuring a fl eet’s vehicles stay on the
road and out of the shop.
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