Exhaust Brake Operation

The exhaust brake may not seem to work properly on some 2020 Silverado and Sierra models equipped with the 6.6L Duramax diesel engine (RPO L5P). No DTCs will be set.

The exhaust brake system, which can be used to provide additional braking when the vehicle is decelerating with a heavy load and/or down a steep grade, is activated using a driver-selected switch. (Fig. 19) The Engine Control Module (ECM) controls exhaust brake operation based on various sensor inputs and commands the turbocharger vane position to maximum boost for exhaust brake operation.


Fig. 19


New Calibrations may be Available

For the 2020 model year, the movement of the turbocharger vanes is slower than in previous models and, as a result, there may be a feeling that the exhaust brake is not operating correctly. If the exhaust brake does not seem to be working properly, check for any ECM or Transmission Control Module (TCM) calibration updates that may be available. For additional information, refer to Bulletin #21-NA-214.

If available, both ECM and TCM calibration updates should be performed in order to enhance the operating feel of the exhaust brake.

If the TCM is updated without updating the ECM, the enhancements to the operation of the exhaust brake may not be felt. In addition, if only the ECM is updated without updating the TCM, the vehicle may operate in reduced power mode with communication codes set as the engine and transmission may not be able to communicate properly.


Exhaust Brake Details

For additional customer information, refer to the following exhaust brake description from the Owner’s Manual:

  • Automatic downshifts will not occur if the vehicle is in Range Selection Mode. See Manual Mode in the Owner’s Manual.
  • The exhaust brake only activates when the transmission torque converter is locked. This can vary based on vehicle speed, gear, and load.
  • To activate the system, press the Exhaust Brake button on the center stack. A light in the switch will come on when the exhaust brake is activated. The switch must be pressed at each vehicle start for the system to be active. The Driver Information Center (DIC) displays the message Exhaust Brake On for approximately three seconds, and then clears.
  • To turn the exhaust brake off, press the exhaust brake switch a second time. The DIC displays the message Exhaust Brake Off for approximately three seconds, and then clears.
  • The exhaust brake will be more active when in Tow/Haul Mode.


– Thanks to Scott Willems

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