Failure mode - Cummins 6.7L ISB Diesel (Ram HD)

Holset VGT turbo sticking / actuator failure

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

Symptoms

loss of exhaust-brake function (the classic first sign - the VGT is the exhaust brake)
low power / boost DTCs (over/underboost), smoky acceleration
turbo actuator DTCs; 'Service Electronic Throttle'?
excessive idle/lope or whistle change; failed regens because the turbo cannot build regen heat

Compare with the other causes of the same sign on this engine: loss of power, limp mode or derate (6 causes) · black smoke or smoke under load · ticking, knocking, rattle or whine (7 causes) · misfire, rough idle, hesitation or surging (5 causes) · def, dpf and regeneration warnings (4 causes)

Root cause

The electronically-actuated Holset variable-geometry turbo (HE351VE 2007.5-2012 pickups, HE300VG 2013+ pickups) moves its nozzle vanes for boost control, exhaust braking and DPF regen heat. Soot from regens and EGR fouls the vanes/unison ring; the electric actuator is exposed to heat and fails independently. Wikipedia's B-Series article calls the VGT 'an extremely common issue' typically flagged by exhaust-brake loss.

Diagnosis

actuator/nozzle-position DTCs and live vane-position PID vs commanded - stuck or lagging vane position is the tell
test the exhaust brake at cold start: no RPM dip / braking effect = nozzle not closing
inspect vane motion with the actuator commanded (shop tool); look for soot coke in the turbine housing
rule out boost leaks (boots, CAC) before condemning the turbo

Fixes

replace the electronic actuator alone when vanes move freely but the actuator is dead (cheaper than a turbo) ()

6.7 Cummins VGT Electronic Actuator

reman/upgrade turbo (HE351VE-family reman or bolt-on upgrade; 2013+ HE300VG unit) ()

vgt-turbo - more than one option: Holset HE351VE VGT Turbo (2007.5-2012 pickup), Holset HE351VE VGT Turbo - Mopar Reman (2007.5-2012 pickup, current PN R8048234AI), Holset HE300VG VGT Turbo (2013-2018 pickup)

address the soot source: duty cycle / regen health and EGR condition, or the replacement turbo will coke too ()

6.7 Cummins EGR Valve

Prevalence

very-common

Parts for this repair run about $3,250-$6,000: see them next to the other repairs on this engine in repair costs.