TSB 661.20 — Cadillac, Chevrolet and GMC Software update
661.20 is a software update on file with NHTSA for 9 Cadillac, Chevrolet and GMC models, 2024–2027 model years, filed and re-filed as 7 documents. A TSB is factory repair guidance, not a recall — the repair is not automatically free.
What the bulletin says. • This update contains a required software change to help improve the overall software update and diagnostics process. Be sure to install this update to be able to receive future software updates. • Improves traction and stability control when accelerating or on uneven terrain.…
NHTSA's own summary of the document, quoted from the public manufacturer-communications file.
Worth checking your VIN against. 661.20 is filed as a software update, which unlike an ordinary bulletin can mean free or reimbursed work when a vehicle qualifies. Ask a dealer using the document ID below, and check open recalls separately at nhtsa.gov/recalls.
Vehicles and model years 661.20 names
Every document filed under 661.20
Manufacturers re-issue a bulletin as the repair changes, and file separate copies for technicians and for owners. All of them carry the same number.
| Document ID | Filed | Type |
|---|---|---|
| 661.20 | June 10, 2026 | Software update |
| 661.20 | May 1, 2026 | Software update |
| 661.20 | April 14, 2026 | Software update |
| 661.20 | April 14, 2026 | Software update |
| 661.20 | April 10, 2026 | Software update |
| 661.20 | March 27, 2026 | Software update |
| 661.20 | March 2, 2026 | Software update |
Questions buyers ask
What is TSB 661.20?
661.20 is a software update filed with NHTSA by Cadillac, Chevrolet and GMC, covering 9 Cadillac, Chevrolet and GMC models across the 2024–2027 model years. NHTSA's summary reads: • This update contains a required software change to help improve the overall software update and diagnostics process. Be sure to install this update to be able to receive future software updates. • Improves traction and stability control when accelerating or on uneven terrain.…
Which vehicles does 661.20 cover?
NHTSA's file names Cadillac Escalade (2024, 2026); Chevrolet Bolt EV (2027); Chevrolet Corvette (2024–2025); Chevrolet Equinox (2025–2026); Chevrolet Silverado 2500 (2025); Chevrolet Suburban (2024, 2026); Chevrolet Tahoe (2024, 2026); GMC Terrain (2025–2026); GMC Yukon (2024, 2026). A bulletin number can be re-issued against more vehicles later, so check the model-year list on this page against your own.
Is TSB 661.20 a recall, and is the repair free?
661.20 is filed as a software update, not a recall — but this is the kind of communication that can mean free or reimbursed work if your VIN qualifies. Take the number to a dealer and ask. Recalls are separate and always free; check yours by VIN at nhtsa.gov/recalls.
How do I get the full text of 661.20?
Take the document ID to a dealer's service desk, or search NHTSA's manufacturer-communications records. This page carries every document ID filed under 661.20, its date, and NHTSA's own summary from the public file.
Every number on this page is a count of records in the federal complaint, recall, and investigation files published by NHTSA's Office of Defects Investigation. This page lists only what NHTSA's manufacturer-communications file records under 661.20. Check any specific vehicle's open recalls by VIN at nhtsa.gov/recalls.