[doughboy]

It is a known PUMA case with BMW, says it should be investigated if the customer complains, the fix is listed as replace and retorque exhaust cam retainer bolts

I paid for mine to be fixed by an independent BMW specialist garage when BMW fobbed me off. Mine was clearly a single lifter, 1 knock every 2 engine revs, quite slow but metallic, tick, tick, tick at idle. Very noticeable even my wife would say "what's that noise?".

Not injectors. They operate 6 times per 2 engine revs. Get an engine stethoscope and
Put it near no.1 exhaust end you'll hear it!

Nobody will have codes for this FFS if you know anything about engines.

Since it was fixed it's perfectly quiet hot and cold.