Mending GMC low voltage condition

July 9, 2024
This bulletin applies to 2017-2018 GMC Sierra and 2019-2021 Sierra 2500HD/3500HD trucks equipped with an L5P turbocharged diesel engine.

This bulletin applies to 2017-2018 GMC Sierra and 2019-2021 Sierra 2500HD/3500HD trucks equipped with an L5P turbocharged diesel engine. The MIL may be on. DTC P0046 (turbocharger boost control position performance) may be set in the ECM.

This condition may be caused by a low voltage condition during cranking that does not allow the turbocharger to complete the turbo actuator learn procedure.

Note: The M103 turbocharger vane position actuator arm is returned to the top rest position by a spring inside the actuator. A small amount of spring resistance is normal. The M103 turbocharger vane position actuator arm rest position is vertical. The arm bottom of travel position is horizontal.

Turn ignition off, close all doors and wait for two minutes. Verify that the turbo actuator arm can easily be pushed down from the top rest position without binding to the bottom of travel position. Verify that the return spring returns the actuator arm to the top rest position.

If the turbocharger and actuator are working as designed, perform a relearn using GDS2 (module diagnostics, engine control module, configuration/reset functions, learn functions, turbo boost control initial position learn).

Perform the scan tool control function: turbocharger vane position = the value should increase and decrease according to the setting on the scan tool. If this corrects the condition, both of the batteries should be checked individually for low voltage.

About the Author

Motor Age Staff

Motor Age has been publishing technical content for professional automotive technicians since 1899. Our writers have decades of experience and scores of ASE certifications, and they continue to teach new generations of technicians via classrooms all around the globe, as well as through the books and training manuals they've authored. 

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