A063A617 | Genuine Cummins® Decomposition Reactor 15L ISX/QSX

Convert DEF into ammonia

• When DEF is injected into the hot exhaust, the decomposition reactor helps break it down into ammonia (NH₃).

Support the SCR system

• The ammonia produced is used in the Selective Catalytic Reduction (SCR) catalyst to remove harmful gases.

Reduce nitrogen oxide (NOx) emissions

• Ammonia reacts with NOx gases and converts them into harmless nitrogen and water vapor.

Improve emissions control

• Helps diesel engines meet environmental emission regulations.

Ensure proper DEF mixing

• The reactor allows DEF to mix evenly with exhaust gases before reaching the SCR catalyst.

Check Engine Light

• The engine computer may detect abnormal emissions or SCR system problems.

SCR / Emissions warning message

• You may see warnings like “SCR Fault”, “Emissions System Problem”, or “Service DEF System.”

High NOx emissions

• If the reactor cannot properly break down DEF into ammonia, the system cannot reduce NOx gases effectively.

Poor DEF system performance

• The vehicle may show DEF dosing errors or inefficient SCR operation.

Derate or reduced engine power

• Some diesel trucks limit engine power (engine derate) when emissions components fail.

Excess DEF deposits

• You may see white crystal deposits in the exhaust if DEF is not decomposing correctly.

Failed emissions test

• Vehicles may fail emissions inspections due to improper NOx reduction