06/02/2026
Vehicle presented with complaints of reduced power, frequent regeneration events, and elevated exhaust backpressure. Diagnostic testing revealed the Diesel Particulate Filter (DPF) was severely face-plugged with soot and heavily contaminated with ash deposits, restricting exhaust flow through the filter substrate. Differential pressure readings across the DPF were significantly above specification, confirming excessive restriction within the aftertreatment system.
Further diagnosis identified a leaking EGR cooler as the root cause of the failure. Coolant entering the exhaust stream through the failed EGR cooler introduced contaminants into the aftertreatment system, accelerating ash accumulation and contributing to severe face plugging of the DPF. The resulting restriction prevented effective regeneration, increased exhaust backpressure, reduced engine performance, and placed additional stress on the turbocharger and exhaust aftertreatment components.
Corrective action includes replacement of the failed EGR cooler, replacement of the DPF assembly, inspection of related aftertreatment components for coolant contamination, and verification of proper EGR and exhaust system operation. Following repairs, all applicable aftertreatment adaptations and learned values should be reset, and the vehicle should be road-tested to confirm normal exhaust backpressure, regeneration performance, and overall engine operation.
