BMW B38 (1.2 and 1.5)
1.5 L · inline-3 · turbocharged · petrol · 2013–present
Also known as: b38a15, b38k15, 1.5 turbo three-cylinder, 1.5 turbo, cooper engine, 118i engine, b38a15m0, b38a12
The three-cylinder end of BMW's modular family, sharing its architecture with the four-cylinder B48 and the straight-six B58. All three are built around the same 500 cc cylinder, which is why a MINI Cooper, a 320i and an M340i share service intervals, sensors and a great deal of the diagnostic picture — a fault pattern learned on one is often worth reading across.
Three cylinders cannot balance themselves, so it carries a balance shaft; the vibration a driver notices at idle is normal for the layout rather than a symptom. It also introduced the first aluminium turbine housing fitted to a production turbocharger.
Its range is wider than the badge suggests. The same engine appears at 74 hp in a base 1 Series and at 228 hp in the i8, where it drives the rear axle of a plug-in hybrid — so a power figure quoted for "the 1.5" says very little without the car it came in.
The published fault picture is thin, which is worth stating plainly rather than filling in: this engine has not accumulated the documented, recall-backed failure modes of the N63 or the N47, and the honest answer today is that its common problems are not well established.
Cars fitted with this engine
13 generations, across 2 makes. From the authored catalogue — an absent car means the catalogue has not reached it, not that the engine was never fitted.
BMW
Information, not instruction
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Posted about this engine
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Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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