TSB: Buick Encore Mystery DTC

This bulletin applies to 2024-2025 Buick Encore GX vehicles. The CEL/MIL may be illuminated along with a service charging system message. DTC P0621 may be set as current or history. GM engineering is currently investigating this issue. Follow the diagnostic procedures outlined in the service manual for the DTC. If the test results do not directly identify a functional fault other than a warning message/light, do not replace any parts at this time. Advise the customer that they may continue to drive the vehicle.