The brief
Mr Poh's X1 was throwing an engine oil warning and a stored fault code, so he brought it in. An oil warning is one you never ignore, low oil wrecks an engine fast, so the first job is to confirm whether the oil really is low or the car is misreading it. BMW doesn't fit a dipstick on a lot of these, it reads the oil level electronically with a sensor in the sump and shows it on the dash. That sensor sits in hot oil for years and eventually drifts or fails, and when it does it reports a level that isn't real, so the dash warns of low oil and logs a fault even though the sump is full. A failed sensor doesn't come back, so once the oil's confirmed good, the sensor gets replaced.
The diagnosis
We checked the actual oil level and condition first, it was full and clean, no leak, no consumption. Diagnostics read the stored fault and the live data showed the oil level sensor reading wrong, which is the false low-oil warning. The engine and the rest of the system were fine. That's an oil level sensor replacement, rather than chasing a leak or a consumption problem that wasn't there.
The work
The oil was drained enough to get at it, the old oil level sensor removed from the sump and a new genuine BMW-spec sensor fitted with a fresh seal, then the oil refilled to the correct level. The fault was cleared and the system checked to be reading the level correctly on the dash. A road test confirmed the warning stayed off and the dash showed the right level.
The outcome
No oil warning, no stored fault, the dash reading the correct oil level, and the engine running fine on a sump that was always full. The X1 went home with the false alarm sorted. Confirming the oil was good before swapping the sensor meant we fixed the actual fault rather than a leak that didn't exist, so it was one visit and done.