Headlamps, halogen composite, flash-to-pass, automatic on and off

Years 2011 Models 2

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Also described as Headlamps, halogen composite, Twilight Sentinel, flash-to-pass

Also documented for Chevrolet GMC

Documented applications

LaCrosse — Epsilon II, 2nd gen (2010–2016)

2011 Confirmed

2011: recoded T4A for 2012 per GM Authority 2012 RPO list

Regal — Epsilon II, 5th gen (2011–2017)

2011 Confirmed

recoded T4A for 2012 (GM's 2012 list)

This page aggregates every documented appearance of TT4 in the Buick reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.