The particulates in the exhaust gases are collected by the diesel particulate filter (DPF). When the filter becomes saturated with particulates, they are incinerated by a regeneration process. The regeneration process increases the exhaust gas temperature, warming the diesel oxidation catalyst (DOC) first, then warming the DPF. The engine control module (ECM) monitors the system with inputs from two exhaust gas temperature (EGT) sensors 1 and 2 and an exhaust differential pressure sensor.

The ECM will command an active regeneration base on a calculated soot model. The soot model calculations are based on the following information:

If the ECM detects that the average time between completed regenerations is less than a calibrated threshold this diagnostic will fail.

The ECM detects that the average time between completed regenerations is less than 1 hour 10 minutes.

DTC P2459 is a Type A DTC.

DTC P2459 is a Type A DTC.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Description and Operation Reference

Diesel Particulate Filter (DPF) System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Special Tools

1. Verify that DTCs P003A, P0047, P0048, P0087, P0101, P0201-P0208, P02A1, P02A5, P02A9, P02AD, P02B1, P02B5, P02B9, P02E0, P02E7-P02E9, P029D, P0234, P0299, P0300-P0308, P0401, P0402, P046C, P0545, P0546, P0698, P0699, P2032, P2033, P2269, P2453, or P2563 are not set.

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

2. Engine running at a warm stabilized idle, observe the scan tool Particulate Filt. Pressure Variance parameter. The value should be between 0-3 kPa.

Important: 

•	Perform the Repair Verification after completing the Circuit/System Testing.

•	DO NOT clear this DTC until the repair is completed. This DTC will take several hours and/or miles to reset.

•	Select Capture Info to store the DTC information with the scan tool.

•	This DTC may require reviewing the Freeze Frame/Failure Records carefully for accurate diagnosis.

1. Visually inspect the exhaust differential pressure system for any of the following conditions:

•	Modifications

•	Damaged components

•	Loose or improperly installed components--Ensure the smaller diameter pressure line is connected to the front of the DPF and to the smaller port of the differential pressure sensor.

•	Improperly routed differential pressure lines--The exhaust differential pressure line should have a continuous downward gradient without any sharp bends or kinks from the sensor to the DPF.

2. Remove and visually inspect the flexible part of the exhaust differential pressure lines for internal restrictions.

⇒	If a condition is found, replace the exhaust differential pressure lines.

3. Test for water in fuel contamination. Refer to Contaminants-in-Fuel Diagnosis .
4. Ignition ON, observe the scan tool EGR Position Sensor and Desired EGR Position parameters while commanding the EGR solenoid to 20 percent and 0 percent. The values should remain equal to or less than 3 percent.

⇒	If greater than the specified range, replace the EGR valve and gaskets.

5. Engine running, verify the scan tool Particulate Filt. Pressure Variance parameter is greater than 0 kPa (0 psi) and increases as engine speed is increased.

⇒	If less than the specified range, and the parameter decreases as engine speed is increased, inspect for incorrect differential pressure line routing.

6. Test the charge air cooler (CAC) for leaks. Perform the Full System Air Leak Test and Induction System Smoke Test. in Charge Air Cooler Diagnosis .
7. Test the fuel system for leaking fuel injectors, high fuel pressures, or high fuel injector flow rates. Refer to Fuel Injector Balance Test with Tech 2 .
8. Ignition OFF, disconnect the harness connector at the exhaust differential pressure sensor.
9. Ignition OFF and scan tool disconnected for 90 seconds, test for less than 5 ohms between the low reference circuit terminal 1 and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

10. Disconnect the harness connector X1 at the ECM.
11. Test for less than 5 ohms on the differential pressure sensor circuits between the following terminals:

•	ECM X1 5-volt reference circuit terminal 14 to exhaust differential pressure sensor terminal 3.

•	ECM X1 signal circuit terminal 43 to exhaust differential pressure sensor terminal 2.

⇒	If greater than the specified range, repair the affected circuit for an open/high resistance.

12. If all circuits, exhaust system, and engine control system components test normal, test or replace the exhaust differential pressure sensor.

Important: You must perform the Circuit/System Testing in order to verify the integrity of the exhaust differential pressure sensor circuits before proceeding with Component Testing.

1. Ignition OFF, remove the exhaust pressure differential pressure sensor.
2. Install a 3A fused jumper wire between the 5-volt reference circuit terminal 3 and the corresponding terminal of the differential sensor. Install a jumper wire between the low reference terminal 1 of the sensor and ground.
3. Connect a DMM between terminal 2 of the differential sensor and ground.
4. Ignition ON, with the J 23738-A or J 35555 connected to the pressure sensor rear pressure port, slowly apply vacuum to the sensor while monitoring the voltage. The voltage should vary and transition smoothly without any spikes or dropouts.

⇒	If the voltage is erratic, replace the differential pressure sensor.

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) Regeneration Enable .