PEC017
5/3/2018
Page
86
of
105
20.0
Manual HC Desorb
Overview
HC Desorb functionality is necessary to protect the aftertreatment from damage after
extended idling. Idling a truck results in low exhaust temperatures and low exhaust
flows, which promotes unburned hydrocarbons in the exhaust to absorb onto catalysts
in the aftertreatment. Extended idling presents a risk for aftertreatment damage
because if the aftertreatment catalysts and adsorbed hydrocarbons are brought to
high enough temperatures (by driving the truck) after extended idling, there is a risk of
uncontrolled temperature increase and thermal damage to the aftertreatment
catalysts. After the truck has idled for long enough, there will be enough hydrocarbons
accumulated that is not safe to drive the truck and an HC Desorb will be required. HC
Desorb functionality protects the aftertreatment using controlled exhaust temperature
increase to remove accumulated hydrocarbons in a slow and controlled manner,
allowing the truck to be safely driven after completion.
A Manual HC desorb request, along with a “DO NOT DRIVE” notification, will be
displayed on the dash after the truck has idled long enough that a dangerous amount
of hydrocarbons have accumulated and the truck is NOT safe to drive. At this point, a
Manual HC Desorb must be fully completed to safely remove accumulated
hydrocarbons before the truck can be driven. Failure to comply will result in a P3880
fault and risk of aftertreatment damage.
Manual HC Desorbs are performed by the driver by pressing the regen switch when
the request is displayed on the highline Drivers must complete a Manual HC Desorb
before driving the vehicle if requested.
As long as there is a “DO NOT DRIVE”
notification, do not drive the truck.
All Manual HC Desorb
notifications refer to HC Desorb as a “Regeneration” or
“Regen”. HC Desorb differs from DPF Regenerations in that there is no additional fuel
dosing during an HC Desorb. As a result, tailpipe temperatures will remain below 500
°F (260 °C).
Desorb Notifications on the Driver Display
Figure 20.3 shows an example of the notification displayed when a Manual HC
Desorb is required before driving. If this message is displayed on the dash, the driver
must complete the Mnaual HC Desorb before driving the truck. This applies to both
Peterbilt and Kenworth on non-VECU, NAMUX 2 & 3 trucks.
Figure 20.3
– NAMUX 2 & 3 Manual HC Desorb Required Notification; Left: Kenworth, Right: Peterbilt
