OnStar Protect, 12 months

Years 2025–27 Models 4 Factory citations 13

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Also described as OnStar Protect, 12 months of service

Also documented for Cadillac Chevrolet GMC

Documented applications

Enclave — VSS-S (2025–2027)

2025–2027 Factory-verified

O on all trims; fleet plan; the 2025 guide names it OnStar Security

GM factory document — 2025 buick all new enclave fleet order guide, p.29.
GM factory document — 2026 buick enclave fleet order guide, p.30.
GM factory document — 2027 buick enclave fleet order guide, p.30.

Encore GX — VSS-F (2020–2027)

2025–2027 Factory-verified

Preferred, Sport Touring, Avenir: O; the 2025 guide names the plan OnStar Security

GM factory document — 2025 buick encore gx fleet order guide, p.30.
GM factory document — 2026 buick encore gx fleet order guide, p.33.
GM factory document — 2027 buick encore gx fleet order guide, p.31.

Envision — E2XX (2021–2027)

2025–2027 Factory-verified

2027: all trims: O; the 2025 list reads OnStar Security - 12 Months of Service; the 2026–2027 lists name the plan differently

GM factory document — 2025 buick envision fleet order guide rpo codes, p.1.
GM factory document — 2027 buick envision fleet order guide rpo codes, p.1.
GM factory document — 2027 buick envision fleet order guide, p.25.

Envista — VSS-F (2024–2027)

2025–2026 Factory-verified

all trims: O; the 2025 list calls it OnStar Security, 12 months of service

GM factory document — 2025 buick envista fleet order guide rpo codes, p.1.
GM factory document — 2025 buick envista fleet order guide, p.22.
GM factory document — 2026 buick envista fleet order guide rpo codes, p.1.
GM factory document — 2026 buick envista fleet order guide, p.24.

This page aggregates every documented appearance of P0U in the Buick reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.