Half an hour behind the wheel — and suddenly almost no air comes from the vents. The fan may be roaring at full speed, yet the cabin still turns stuffy. General Motors has already issued preliminary service document PIC6660, but there is an awkward catch: engineers are still looking for the definitive cause, and there is no final repair procedure yet.
And the issue is much broader than a story involving just a couple of Buick models. PIC6660 covers four crossovers — the Buick Envista, Encore GX, Chevrolet Trax and Trailblazer from the 2024–2026 model years in North America. There are no engine or transmission restrictions. The document lists climate-control systems with RPO codes C60, C67, C68 and CJ2.
The main suspect has already emerged — the air-conditioning evaporator. After more than half an hour of continuous driving, it can ice up so heavily that the ice effectively blocks airflow through the HVAC unit. That is why simply turning up the fan changes nothing: the air has nowhere to go.
What should the dealer do? First, check the refrigerant charge. If it is low, GM instructs technicians to find the source of the leak and repair it using the standard service procedure. But if the charge is correct, things get more interesting: the manufacturer currently advises against replacing parts at random. The engineering investigation is still underway.
This is not a recall campaign. NHTSA classifies PIC6660 as a manufacturer communication — a category that includes bulletins and other automaker notices about defects, failures and irregularities that may or may not be related to safety. GM separately states that the condition described is not currently considered a safety issue.
There is also an intriguing contrast. In J.D. Power ratings for the 2026 model year, the Encore GX scored 90 out of 100 for quality and reliability, while the Envista received 81. A contradiction? Not really. The rating assesses the vehicle as a whole, whereas PIC6660 describes one specific climate-control condition.
All four vehicles are also linked by where they are built. The Envista, Trax, Encore GX and Trailblazer are tied to GM's Korean operations, and the company again emphasized this spring the role of South Korea as one of its key hubs for compact-crossover production and exports.
Now owners are waiting for GM's next move. PIC6660 is expected to be updated once engineers identify the exact cause and prepare a final remedy. Until then, anyone who sees airflow collapse after a long drive with the air conditioning running is better off contacting a dealer and referring to PIC6660 rather than blindly replacing HVAC components.
