GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2007 🢒 Express - AWD 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P1448

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provide an overview of each diagnostic category.

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 filer.

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 DPF regenerations become too infrequent, this diagnostic runs and fails.

Conditions for Running the DTC
    • The engine is running.
    • DTC P1448 runs continuously once the above conditions are 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 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

    •  Engine Controls Connector End Views
    •  Engine Controls Component Views
    •  Engine Control Module Connector End Views

Description and Operation

Diesel Particulate Filter (DPF) System Description

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

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.

⇒If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

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
  1. Install any components or connectors that have been removed or replaced during diagnosis.
  2. Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.
  3. Clear the DTCs.
  4. Turn OFF the ignition for 60 seconds.
  5. 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.
  6. To avoid the customer's return to the service department, perform the Diesel Particulate Filter (DPF) Service Regeneration .