C1.7 and C2.2 Industrial Engine Diesel Particulate Filter Has Low Inlet Pressure Caterpillar

Diesel Particulate Filter Has Low Inlet Pressure

Use this procedure if the following event code is active.

Table 1
J1939 Code and Description  Description  Comments 
3251–1  Aftertreatment #1 DPF Differential Pressure : Low - most severe (3)  The code detects an implausibly low DPF differential pressure which indicates reverse installation of the DPF differential pressure sensor.

The shutdown lamp will illuminate.

The warning lamp will flash fast.

The Emissions Systems Malfunction Lamp will flash fast. 
3251-18  Aftertreatment #1 DPF Differential Pressure : Low - moderate severity (2)  The code indicates the detection of the removal of the DPF substrate.

The warning lamp will flash slowly. 

Table 2
Troubleshooting Test Steps  Values  Results 

1. Inspect the Exhaust System for Leaks

A. Inspect the exhaust system for leaks between the exhaust manifold and the Clean Emissions Module (CEM).

B. Check the exhaust system for loose connections or open ports.

Exhaust Leaks 

Result: The exhaust system has leaks.

Repair: Repair the exhaust. Return the engine to service.

Result: The exhaust system does not have leaks.

Proceed to Test Step 2.
2. Inspect Electrical Connections

A. Inspect the electrical connections between the sensor and ECM for loose wires, breaks, or dirt ingress.
Electrical Connections 
Result: A connection point has damaged wires or pins.

Repair: Repair the damaged wires or pins.

Result: A wire is loose.

Repair: Resecure wire into correct port.

Result: A connection point has excessive dirt/dust.

Repair: Thoroughly clean the connection point and wire ports in the back of the connector with an air gun or similar. Ensure they are free of dirt and/or dust.

Result: Electrical connections have no loose wires, breaks, or dirt ingress.

Proceed to Test Step 3.

3. Inspect the Diesel Particulate Filter

A. Inspect the inlet of the DPF. Inspect the DPF for a missing or damaged DPF brick.
Damaged DPF Brick 
Result: The DPF has a damaged or missing DPF brick.

Repair: Replace the damaged DPF or missing DPF brick. Return the engine to service.

If the procedure did not correct the issue, contact the Dealer Solutions Network (DSN).

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