API Starter, 36 months

Years 2022–23, 2026–27 Models 5 Factory citations 11

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Also described as OnStar Assurance for Tier 3 fleets, 45 months added

Also documented for Cadillac Chevrolet GMC

Documented applications

Enclave — C1XX (2018–2024)

2022–2023 Factory-verified

all trims: O; fleet orders

GM factory document — 2022 buick enclave order guide copy nhtsa docket, p.37.
GM factory document — 2023 buick enclave order guide copy autoevolution wayback, p.35.

Enclave — VSS-S (2025–2027)

2026–2027 Factory-verified

O on all trims; fleet telematics data plan

GM factory document — 2026 buick enclave fleet order guide, p.40.
GM factory document — 2027 buick enclave fleet order guide, p.40.

Encore GX — VSS-F (2020–2027)

2026–2027 Factory-verified

Preferred, Sport Touring, Avenir: O

GM factory document — 2026 buick encore gx fleet order guide, p.46.
GM factory document — 2027 buick encore gx fleet order guide, p.44.

Envision — E2XX (2021–2027)

2026–2027 Factory-verified

2027: all trims: O

GM factory document — 2026 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.35.

Envista — VSS-F (2024–2027)

2026 Factory-verified

all trims: O

GM factory document — 2026 buick envista fleet order guide rpo codes, p.1.
GM factory document — 2026 buick envista fleet order guide, p.34.

This page aggregates every documented appearance of P1U in the Buick reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.