Failure mode - Cummins 5.9L Diesel (Dodge Ram HD)

Turbo wastegate actuator seize / boost control (HX35W, HE351CW)

Reliability tier: aggregated - verify before ordering, see /disclosure/

Symptoms

overboost spikes and defuel (actuator seized closed); or lazy spool and low boost (stuck open)
hot-side carbon binding after long idle-heavy service

Compare with the other causes of the same sign on this engine: loss of power, limp mode or derate (4 causes)

Root cause

The free-floating turbos rarely die; it is the wastegate actuator and its carbon-bound linkage that stick, either overboosting (defuel) or bleeding boost. Follows the same actuator-first diagnosis as every Cummins turbo generation.

Diagnosis

gauge the boost against target; exercise the actuator arm by hand cold and note the binding point
check the actuator line for cracks and carbon in the swing valve

Fixes

free/replace the actuator; rebuild kit or a reman turbo when the shaft play is out of spec ()

Prevalence

occasional