The 2019 GMC Sierra 2500's Duramax features an exhaust brake for improved engine braking when towing. When the exhaust brake doesn't engage or provides reduced braking, towing control is compromised.
How the Exhaust Brake Works
The Duramax exhaust brake uses the Variable Geometry Turbo (VGT) to restrict exhaust flow, creating back pressure that slows the engine. This supplements mechanical brakes when descending grades with heavy loads.
Causes of Exhaust Brake Problems
VGT Actuator Issues
The VGT actuator controls vane position for both boost and exhaust braking. Actuator problems prevent proper vane closure needed for exhaust restriction.
Stuck or Sooted Vanes
Carbon buildup can prevent VGT vanes from closing fully. This reduces exhaust restriction and braking effectiveness.
System Disabled Due to Faults
The exhaust brake won't engage if the system detects related faults. DPF, DEF, or EGR problems may disable exhaust brake function.
Incorrect Activation
The exhaust brake has specific activation conditions. Ensuring proper switch activation and tow/haul mode may be necessary.