GM addresses heater issue in 2025-2026 full-size models
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GM's NHTSA bulletin PIT6452C addresses heater malfunctions in 2025-2026 GMC, Chevrolet, and Cadillac models. Learn about the HVAC defect and repair procedures.
General Motors has issued an updated service bulletin, PIT6452C, through the National Highway Traffic Safety Administration (NHTSA), addressing a heater malfunction in certain full-size 2025 and 2026 models.
The issue affects the GMC Sierra 1500, Yukon, and Yukon XL, along with related Chevrolet and Cadillac models. Owners report that when the front-seat heating is activated, cold air may blow despite a warm cabin. In some cases, a clicking sound from the instrument panel accompanies temperature changes, and the system logs fault codes B2B05 or B2B29.
GM engineers determined the cause to be a manufacturing defect in the HVAC system's temperature blend door. An irregularity on a plastic component can cause binding, linkage detachment, or actuator stoppage.
For diagnosis, dealers must use an endoscope to check the door's full range of motion. If a defect is found, the upper evaporator case assembly requires replacement, followed by actuator adaptation using the GDS 2 system. GM emphasizes that this bulletin is intended for professional technicians and is not designed for DIY repairs.
