# Over\-the\-air update 662.21

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

- Type: Over\-the\-air update
- NHTSA id: 11036471
- Published by NHTSA: 2026\-08\-31
- Manufacturer's number: 662.21
- Manufacturer's date: 2026\-08\-05
- Campaign id or software version: 662.21
- NHTSA component: UNKNOWN OR OTHER
- Manufacturer's system: BCM, TCM, ECM: BCM \(Body Control Module\), TCM \(Transmission Control Module\), ECM \(Engine Control Module\)

## NHTSA's summary

• Fixes to help ensure proper functionality for heating and cooling features. • Improvements to night mode lights for shifting gears. • Fixes for Daytime Running Lamps turning on when set to Off. • Fixes to help prevent erroneous missing key messages on driver display. • Fixes for accuracy of low tire pressure alert. • Fixes for speed threshold for pedestrian alerts. • Improvements to start reliability and reduced check engine light activation • Improvements to turbo system diagnostics • Improvements to reliability when extending the running boards on your vehicle • Improves transmission diagnostic software. • Reduces unnecessary check engine light activations. • Fixes to help extend coolant valve life through diagnostic changes

## The document

- [NHTSA's copy of the document (PDF)](https://static.nhtsa.gov/odi/tsbs/2026/MC-11036471-0001.pdf)
- [If that address does not open, try this one](https://static.nhtsa.gov/odi/tsbs/2026/MC-11036471-9999.pdf)

The document is the manufacturer's. This site does not hold it.

## Vehicles listed

- 2025 CHEVROLET SILVERADO 1500
- 2025 GMC SIERRA 1500

JSON: [/v1/bulletins/11036471](/v1/bulletins/11036471)

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