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Since there has been a lot of people on here with confusion on what an active/passive regen is, and how that all functions on our trucks, I decided to help everyone out and post what the tech manual says.


Passive regeneration occurs when the exhaust temperatures are naturally high enough to oxidize the soot collected in the die- sel particulate filter faster than the soot is collected.
Passive regeneration typically occurs when the temperature of the diesel particulate filter is above 300°C (572°F). This occurs during highway driving or when driving with heavy loads.
Since passive regeneration occurs naturally, it is considered to be normal engine operation. No fuel is added to the exhaust stream during passive regeneration.


Active regeneration occurs when the exhaust temperatures are not naturally high enough to oxidize the soot collected in the Diesel Particulate Filter (DPF) faster than it is collected.
Active regeneration requires assistance from the engine in order to increase the exhaust temperature. This is typically done by injecting a small amount of diesel fuel into the exhaust stream, which is then oxidized by the diesel oxidation catalyst. The oxi- dation of this additional fuel raises the exhaust temperatures to approximately 550°C (1,022°F), which is needed to regenerate the DPF.
For active regeneration to occur, the Engine Control Module (ECM) must detect that the DPF restriction has reached a speci-fied limit. Once this limit is reached, the engine will alter its operation in order to create exhaust tempera- tures high enough to actively regenerate the DPF.


ACTIVE/STATIONARY REGENERATION
• During active regeneration, the engine ECM monitors the exhaust temperatures before and after the diesel
particulate filter and maintains the temperatures in a range of approximately 482 to 649°C (900 to 1,200°F). The quantity of fuel used for aftertreatment injection will vary as the temperature is controlled within these limits.
• The temperatures achieved during active regeneration are typically higher than those achieved during pas- sive regeneration. The conversion of soot to carbon dioxide occurs much faster as temperatures increase.
• A typical active regeneration event will take approximately 20 to 40 minutes to complete while the vehicle is
operating. The vehicle operator may notice additional turbocharger noise during this time.
• The frequency at which an engine will require an active regeneration varies greatly from application to appli- cation. In general, vehicles with a low vehicle speed, such as urban vehicles or a low-load duty cycle, will require more active regeneration events than a heavily loaded vehicle or a vehicle with a highway speed
duty cycle.
• The engine ECM also contains a time-based feature for active regenerations, which is used to verify correct
operation when the vehicle duty cycle is typically high enough that active regeneration events are not neces-
sary.
• If the engine has not completed an active regeneration within the last 24 hours of operation, the engine ECM
will call for a time-based active regeneration event.
• The 24-hour timer resets each time the ECM detects that an active regeneration event has completed.
• Under some operating conditions, such as low-speed, low-load, or stop-and-go duty cycles, the engine may
not have enough opportunity to regenerate the diesel particulate filter during normal vehicle operation. When this occurs, the engine illuminates the diesel particulate filter lamp to inform the vehicle operator that assis- tance is required, typically recommending to alter the duty cycle to a highway speed duty cycle for approxi- mately 30 minutes. If the lamp persists after altering the duty cycle, the vehicle will require a stationary regeneration. Refer to EC-182, "Aftertreatment DPF Regeneration Test".
• If the engine needs to initiate an active regeneration event, but the vehicle speed is zero and the engine is at low idle speed, the engine will not immediately enter an active regeneration event. The ECM will wait until the engine speed increases to begin the active regeneration event. Once the active regeneration begins, and the exhaust temperatures have increased, the engine will maintain the active regeneration event, even if the vehicle speed returns to zero and the engine speed returns to idle.
• If the engine needs to initiate an active regeneration event, but the vehicle speed is zero, the engine will not immediately enter an active regeneration event. The ECM will wait until the vehicle speed is above 8 km/h (5 mph) before beginning the active regeneration event. Once the active regeneration begins and the exhaust temperatures have increased, the engine will maintain the active regeneration event, even if the vehicle speed returns to zero and the engine speed returns to idle. However, the temperatures being targeted are lowered if the vehicle speed drops below 8 km/h (5 mph).
• When the vehicle speed is greater than 8 km/h (5 mph), an active regeneration event can occur at any time.
• If a vehicle has a low vehicle speed or stop-and-go duty cycle, the engine may not have enough opportunity to perform or complete an active regeneration event. An engine in this situation can illuminate the diesel par-
ticulate filter lamp on a frequent basis, signaling the need for assistance.
• The aftertreatment warm-up feature activates during periods of extended idle time.
• The purpose of this feature is to increase the temperature of the aftertreatment system to remove any water
condensation that has built up during the idle time.
• After the ECM detects that the exhaust temperature entering the aftertreatment system has been below
150°C (302°F) for approximately 2 hours, the ECM automatically increases the engine speed to between
1,000 and 1,100 rpm for approximately 10 minutes.
• For the aftertreatment warm-up feature to activate, the following conditions must be met:
  • The brake pedal is released.
  • The transmission is in N (neutral) or P (park).
  • The vehicle speed is zero.
  • The accelerator pedal is released.
• The aftertreatment warm-up feature is similar to stationary service regeneration because it uses the same
engine speeds and inputs. However, the aftertreatment warm-up feature does not require aftertreatment injection as it does not require the higher temperatures that are needed during stationary service (parked) regeneration.
• Increasing the exhaust temperature entering the aftertreatment system to above 150°C (302°F) for approxi- mately 10 minutes allows the aftertreatment warm-up to deactivate. This can be done by allowing the engine to operate in this condition for approximately 10 minutes or by driving the vehicle.
 
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