Diagnostic Instructions
DTC Descriptor
DTC P1448: Diesel Particulate Filter Regeneration Frequency Too Low
Circuit/System Description
The particulates in the exhaust gases (solid particles in the exhaust exhibited as black smoke) are collected by the diesel particulate filter (DPF). When the filter becomes saturated with particulates, they are oxidized by incineration. We will refer
to this incineration process as regeneration. When an active regeneration is commanded with the engine control module (ECM) a different engine calibration strategy is used to elevate the exhaust gas temperatures. The first event is to heat up the oxidation catalyst
(DOC). Secondly the particulate filer temperature is elevated. These elevated exhaust gas temperatures incinerate the soot accumulated in the particulate filter.
The ECM will command a regeneration based on a calculated soot model. The soot model calculations are based on a number of different factors including:
| • | Distance since last DPF regeneration |
| • | Fuel used since last DPF regeneration |
| • | Engine run time since last DPF regeneration |
| • | Differential pressure sensor values |
The ECM monitors the DOC and DPF temperatures with inputs from two exhaust gas temperature (EGT) sensors 1 and 2, located before and after the exhaust particulate filter. The ECM also monitors the differential back-pressure in the filter
by a differential pressure sensor.
If the time between completed DPF regenerations become too infrequent, this diagnostic will fail.
Conditions for Running the DTC
| • | DTC P1448 runs continuously when the above condition is met. |
Conditions for Setting the DTC
| • | The engine control module (ECM) detects that the average running of time between the last two completed DPF regenerations is greater than 20 hours, not including idle time. |
| • | The regeneration engine run time trigger is based on a 14 hour threshold. Therefore, the regeneration event was commanded but never completed, causing DTC P1448 to set. |
Action Taken When the DTC Sets
| • | DTC P1448 is a Type A DTC. |
| • | A message center or an indicator may display Clean Exhaust Filter. |
Conditions for Clearing the DTC
DTC P1448 is a Type A DTC.
Diagnostic Aids
| • | This DTC may set if the customer ignores the Clean Exhaust Filter message or indicator and continues to drive the vehicle under conditions that do not effectively clean and/or successfully complete two regeneration events. |
| • | Cold ambient temperatures and short trip driving conditions may cause this DTC. |
| • | Several incompleted regeneration attempts may cause this DTC. |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Diesel Particulate Filter (DPF) System Description
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References
for scan tool information
Circuit/System Verification
Verify that DTCs P003A, P0047, P0048, P0101, P0201-P0208, P02A1, P02A5, P02A9, P02AD, P02B1, P02B5, P02B9, P02E0, P02E7-P02E9, P029D, P0300-P0308, P0402, P046C, P0420, P0545, P0546, P2032, P2033, P244B, P244C, P2463, or P2563 or not set.
Circuit/System Testing
Important: Perform the Repair Verification after completing the Circuit/System Testing.
Verify the integrity of the entire exhaust system by visually inspecting for the following conditions:
| • | Damaged exhaust system components |
| • | Loose or improperly installed exhaust system components |
| • | Leaks, or improperly routed pressure lines--The smaller tube connects to the front of the DPF and the smaller port of the exhaust pressure sensor. The lines should have a continuous downward gradient, without sharp bends, or kinks from the differential
pressure sensor to the exhaust particulate filter assembly. |
Repair Instructions
Diesel Particulate Filter (DPF) Service Regeneration
Repair Verification
- Install any components or connectors that have been removed or replaced during diagnosis.
- Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.
- Clear the DTCs.
- Turn OFF the ignition for 60 seconds.
- Duplicate the Conditions for Running the DTC and use the freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the
Diagnostic Trouble Code (DTC) List - Vehicle
and perform the appropriate diagnostic procedure.
- To avoid the customer's return to the service department, perform the
Diesel Particulate Filter (DPF) Service Regeneration
.
