freightliner S2 Operator's Manual page 68

the DPF, which traps soot particles. If exhaust tem-
perature is high enough, the trapped soot is reduced
to ash in a process called passive regeneration
(regen). Passive regeneration occurs as the vehicle
is driven normally under load; the driver is not even
aware that it is happening. The harder an EPA07 en-
gine works, the better it disposes of soot, as the ex-
haust heat alone is enough to burn the soot to ash.
Over the course of a workday, however, passive re-
generation cannot always keep the ATD filter clean,
so the filter must undergo active regeneration. In
active regeneration, extra fuel is injected into the ex-
haust stream to superheat the soot trapped in the
DPF and turn it to ash. Active regeneration happens
only when the vehicle is moving above a certain
speed, determined by the engine manufacturer. Con-
sult manufacturers' documentation for details.
Both active and passive regeneration happen auto-
matically, without driver input.
Only when operating conditions do not allow for ATD
filter cleaning by at-speed active or passive regen-
eration, the vehicle may require a driver-activated
parked regeneration. The vehicle must be standing
still, and the driver must initiate parked regen. Com-
pleting a parked regen takes 20 minutes to an hour,
depending on ambient conditions.
DANGER
During parked regeneration, exhaust tempera-
tures are very high, and could cause a fire, heat
damage to objects or materials, or personal in-
jury to persons near the exhaust outlet.
Before initiating a parked regeneration, make cer-
tain the exhaust outlets are directed away from
structures, trees, vegetation, flammable materi-
als, and anything else that may be damaged or
injured by prolonged exposure to high heat.
The warning lamps in the driver message center alert
the driver of a regen in progress, of high exhaust
temperatures, of the need to perform a parked regen
either soon or immediately, and of an engine fault
that affects the emissions.
A slow (10-second) flashing of the high exhaust sys-
tem temperature (HEST) lamp indicates that a
parked regen is in progress, and the engine's high
idle speed is being controlled by the engine software,
not the driver.
Exhaust Aftertreatment Systems
A steadily illuminated HEST lamp alerts the operator
of high exhaust temperature during the regeneration
process, if vehicle speed is below 5 mph (8 km/h).
See Fig. 9.2. The HEST lamp does not indicate the
need for any kind of vehicle or engine service; it only
alerts the vehicle operator of high exhaust tempera-
tures. Make sure the engine exhaust pipe outlet is
not directed at any person, or at any surface or ma-
terial that will melt, burn, or combust.
When the HEST lamp is on, be certain that the
exhaust pipe outlet is not directed at combustible
material or toward anyone. To do so could cause
damage to the vehicle and serious personal in-
jury to others.
Active regeneration can occur automatically any-
time the vehicle is moving. The exhaust gas tem-
perature could reach 1500°F (816°C), which is hot
enough to cause a fire, heat damage to objects
or materials, or personal injury to persons near
the exhaust outlet. See Regen-Inhibit Switch later
in this chapter for instructions on preventing au-
tomatic regen if necessary.
The exhaust temperature can remain high even
after the vehicle has stopped. When stopping the
vehicle shortly after an automatic regen, ensure
the exhaust outlets are directed away from struc-
tures, trees, vegetation, flammable materials, and
anything else that may be damaged or injured by
exposure to high heat.
IMPORTANT: Due to the high exhaust tempera-
ture during the regen process, a diffuser is used
to reduce the temperature at the exhaust pipe
outlet. See Fig.
it must be replaced to ensure proper operation
of the vehicle and to reduce the possibility of
damage or injury.
A steadily illuminated yellow DPF lamp indicates a
regen is required soon. Bring the vehicle to highway
speeds to allow for an active regen, or a parked
regen should be scheduled for the earliest conve-
nient time. See
IMPORTANT: Failure to regen could cause en-
gine problems, including derate or loss of
WARNING
WARNING
9.11. If the diffuser is damaged,
Fig. 9.1.
9.8