Chevrolet High Feature V6 (LFX / LY7 / LF1)

GM's High Feature V6 — a 60° all-aluminium design with dual overhead camshafts, four valves per cylinder and variable cam phasing on both intake and exhaust. The LFX is the direct-injected, revised version of the earlier LLT, lighter and with an integrated exhaust manifold in the cylinder head. The family runs from 2.6 to 3.6 litres — LY9, LP1, LF1 and LFW below the 3.6 LY7, LLT and LFX — so the displacement on a badge says which member is fitted and the architecture is common to all of them.

Do not confuse it with the High VALUE V6, which is a different engine: pushrod, 3.5 and 3.9 litres, sold at the same time in some of the same cars. The names differ by one word.

The family's recurring diagnostic theme is the timing system: it uses chains rather than a belt, and stretched chains produce cam-to-crank correlation faults that read as timing codes long before anything is audible. On the earlier LLT, high-pressure fuel pump and timing-chain wear were common enough to be pattern faults, and much of that reputation is inherited by the LFX in owners' minds even where the parts were revised — so establish which member of the family is actually fitted before applying any of it.

Because one design serves six marques, a fault documented on a Cadillac applies directly to a Buick or GMC carrying the same code.