4353361 | Cummins® Inlet Catalyst Module 6.7L ISB/QSB

1. Engine Compatibility

This module is designed for the 6.7-liter displacement family, including:

• Cummins ISB 6.7: Used primarily in on-highway commercial trucks and buses.

• Cummins QSB 6.7: Used in off-road industrial, construction, and agricultural equipment.

• Paccar PX-6 / PX-7: Branded versions of the Cummins 6.7L found in medium-duty trucks.

2. Common Vehicle Fitment

• Medium-Duty Trucks: Freightliner (M2 106), Kenworth (T270, T370), Peterbilt (337, 348), and International (MV Series).

• School Buses: Blue Bird, Thomas Built, and IC Bus models equipped with the ISB 6.7 engine.

• Emergency Vehicles: Fire trucks and ambulances using the 6.7L platform.

• Industrial/Construction: Excavators, loaders, and generators (e.g., Komatsu, Terex, or Cummins Power Generation) using the QSB 6.7 Tier 4 engine.

• Oxidation: It uses precious metals (like platinum or palladium) to convert Carbon Monoxide (CO) and unburnt hydrocarbons into Carbon Dioxide (CO2) and water.

• Heat Generation: It facilitates "Active Regeneration." By oxidizing a small amount of diesel fuel injected into the exhaust stream, it raises the exhaust temperature high enough to burn off the soot trapped in the downstream DPF.

• NO2 Conversion: It converts Nitric Oxide (NO) into Nitrogen Dioxide (NO2), which helps the Selective Catalytic Reduction (SCR) system work more efficiently further down the line.

1. Frequent or Failed Regenerations

The most common sign is that the engine requests "Parked Regen" more often than usual. If the DOC is "face-plugged" (clogged with soot or oil) or chemically depleted, it cannot generate enough heat to burn soot out of the DPF.

2. Fault Codes (Check Engine Light)

You will likely see Cummins-specific fault codes or generic OBDII codes, such as:

• FC1691 / FC1694: Related to low catalyst efficiency.

• FC2639: Indicating the DPF is not regenerating properly due to low inlet temperatures.

• P0420: Catalyst System Efficiency Below Threshold.

3. Increased Backpressure and Power Loss

If the catalyst is physically blocked, the engine will struggle to "breathe." This leads to:

• Noticeable loss of horsepower.

• Poor fuel economy.

• The engine may enter "Limp Mode" (derate) to protect the turbocharger.

4. Visible Damage or Discoloration

• External: Blueing or extreme discoloration of the stainless steel canister indicates severe overheating.

• Internal: If you remove the module, you may see "face-plugging" (a thick layer of black soot on the honeycomb) or physical melting of the ceramic substrate.