If your Chevrolet Silverado 1500 or full-size GM SUV blows toasty heat on one side of the cabin and lukewarm air on the other, you are not imagining it. General Motors has a documented explanation, a diagnostic procedure, and a fix.
The latest revision of GM Preliminary Information bulletin PIT6452E, titled “Poor Heater Performance On Drivers OR Passengers Side,” was added to NHTSA’s public database of manufacturer communications on August 27, 2026. The bulletin walks dealer technicians through diagnosing and repairing binding HVAC temperature doors, the little flaps inside the dash that mix hot and cold air for each side of the cabin.
The Symptoms: One-Sided Heat and a Pop From the Dash
According to the bulletin, owners may notice one or more of the following:
- Reduced heat performance from the driver’s or passenger’s side of the cabin
- A pop noise from inside the HVAC case when adjusting the driver’s or passenger’s temperature setting
- Temperature door binding, which may set one of these diagnostic trouble codes: B2B05, B2B29, B2B07, B2B23, B2B06, or B2B2C
The root cause, per GM: a high spot left on a temperature door during the manufacturing process can cause the door to drag against the HVAC case as it moves through its travel. When the door binds, one side of the cabin stops getting the temperature you asked for, and the strain can even pop the white plastic link that connects the doors right off.
Which Trucks and SUVs Are Covered
PIT6452E applies to GM’s entire full-size lineup for the 2025 and 2026 model years, from work-grade Silverados to the Cadillac Escalade. There is one catch for pickup owners: the bulletin only lists Silverado 1500 and Sierra 1500 trucks with a “G” in the 11th digit of the VIN, which is the assembly plant code for GM’s Silao, Mexico plant. The full-size SUVs, built in Arlington, Texas, are covered across the board.
The bulletin is further scoped to vehicles with climate control RPO codes CJ2 or C67. Not sure what your truck left the factory with? Your glovebox RPO sticker has the answer, and our RPO code guides can help you decode it.
The Fix: Borescope First, Then a New Upper Evaporator Case
This is a two-step job. Technicians first snake a borescope in through the center dash vent (or the evaporator temperature sensor openings) and watch both temperature doors move through their full range of travel. They are looking for binding, resistance, a popping noise, or a temperature door link that has separated from the doors.
If a door misbehaves, the repair is not a minor one: the Heater and Air Conditioning Upper Evaporator Case gets replaced. After the new case is in, the tech cycles the temp doors five to ten times to confirm smooth travel, reinstalls the case, and runs an HVAC actuator learn procedure with the GDS 2 scan tool.
GM lists eight different part numbers for the replacement case depending on body style, engine, and climate system, and instructs dealers to verify the correct one by VIN in the parts catalog:
Not a Recall, So Nobody Is Mailing You a Letter
Here is the part that matters most for owners. PIT6452E is a Preliminary Information bulletin, a diagnostic aid for technicians. It is not a recall, and there is no customer notification campaign attached to it. If your truck has this problem, the only way you would know GM has a documented fix is by reading coverage like this or stumbling onto the bulletin yourself. That is exactly why we track GM technical service bulletins as they surface.
The good news: the repair is covered under the bumper-to-bumper warranty (base warranty in Canada), and GM has already set up a dedicated labor operation (4480958) for dealers to file the claim. Since the affected vehicles are all 2025-2026 models, most should still be well within coverage.
Worth noting for anyone keeping score: this bulletin has been quietly evolving inside GM’s service network since November 2025. The version that just hit NHTSA’s public database is already revision six, with the most recent update on August 21, 2026 touching the warranty section. Translation: dealers have been seeing this one for a while.
What You Should Do
If your 2025 or 2026 Tahoe, Suburban, Yukon, Escalade, Silverado 1500, or Sierra 1500 is blowing uneven temperatures side to side, popping when you adjust the climate control, or throwing any of the B2B-series codes above, mention PIT6452E when you book your service visit. Pointing your advisor to the bulletin can save a diagnostic goose chase and get the borescope into the dash on the first appointment.
Join the Discussion
Has your truck or SUV’s heat or A/C been stuck on one temperature or acting up? Tell us your model year and what your dealer found. Jump into the conversation with fellow owners in our 2019-2026 Silverado 1500 & Sierra 1500 forum or the 2021-2026 Tahoe, Suburban, Yukon & Escalade forum.
Zane Merva is the Executive Editor of GM-Trucks.com and the President of the New England Motor Press Association (NEMPA). A veteran automotive journalist with over 26 years of experience, Zane is a designated ‘Car Talk’ Expert and has been a contributor to The Boston Globe. He possesses a unique evaluative perspective, having road-tested more than 2,000 vehicles across every major manufacturer. While he is a recognized authority on General Motors truck platforms—including the Silverado, Sierra, and Colorado—his expertise is grounded in decades of deep competitive analysis that few in the industry can match. His commentary has been featured by major OEMs and media outlets, including Hyundai and PR Newswire