After a bit of spirited driving in the Canyon, my 2011 Mini Cooper’s CEL came on. Pulling the codes using my OBD reader revealed:
Codes 342 and 343 relate to the camshaft position sensors. When these go wrong the engine management system can’t tell where the crankshaft is, and that can affect performance and emissions. There are two sensors, one for the intake and one for the exhaust, as shown in this diagram from Pelican Parts:
I extracted both sensors (just undo the bolt and pull), after disconnecting each from the wiring harness, and measured the resistance between the three pins on each. The OBD codes indicated that the intake sensor was the problem, and sure enough it measured differently to the exhaust sensor. I ordered two replacement sensors from Amazon, at $19 each:
After fitting the new sensors, the Mini started up with the CEL gone, and performed much better! I had noticed some hesitation when pulling away from a stop, over the last few months, and this has now gone away.