Desperate Trucker Owner.... SCR Melted

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Common Causes Leading to High Exhaust Temperatures and SCR Melting
Several upstream issues can cause these elevated temperatures:

Problems with the DPF — Such as cracking (common in systems with 90-degree outlets), breaching, clogging, or failure to regenerate properly. This leads to incomplete soot burnout, hydrocarbon buildup, and uncontrolled high-heat events during regeneration.
Overfueling or rich running conditions — Often from faulty injectors, turbo issues, or tuning problems, which increase exhaust hydrocarbons and raise temperatures during regen.
Restricted airflow — Due to clogged air filters, intake blockages, or other restrictions, causing incomplete combustion and higher exhaust heat.
Failed regenerations or aftertreatment issues — Including problems in the Diesel Oxidation Catalyst (DOC) or dosing system that allow soot/hydrocarbons to accumulate and burn uncontrollably.
Contaminated DEF (Diesel Exhaust Fluid) — Less directly linked to melting but can contribute to system inefficiencies that indirectly raise temperatures or cause other failures.

Melting is a severe form of damage often discovered during diagnostics for low SCR efficiency codes (e.g., SPN 3582 or P20EE), where the catalyst no longer functions properly. In some cases, earlier Cummins SCR designs had higher failure rates, including recalls for catalyst issues (primarily efficiency, not explicitly melting).
To diagnose, use Cummins INSITE software for SCR efficiency tests, forced regens, and temperature logging. Inspect the DPF/SCR assembly if high temps are suspected. Prevention involves regular maintenance (air filters, DEF quality), monitoring regen frequency, and addressing fault codes promptly. If melting has occurred, the SCR catalyst typically needs replacement (costly, often $4,000+ for OEM).