Hey!
I was about to do my emissions in Washington State and checked for any pending codes and discovered I have a P0300. The code is not a pending but a fault and yet I have no Check Engine Light. I cleared it with a code reader and through the on board diagnostics. Did this several times: clear it and re scan after a minute running the code is still there. Does the car do its self diagnostics that fast? I'm guessing this might be still an issue from the incident described below. Anyone know if RMW tune eliminates limp mode?

Previous to this:
I burned a vale on cylinder 1. No check engine light came on while the car was stumbling. Check engine light come on only when things got really bad and the car barely ran. Car never went into limp mode.
Replaced valve and lapped all the valves. Checked compression 150 +psi on all 4.
Suspected a lean running condition so checked pressure at fuel rail: it was low. Replaced fuel pump and fuel pressure regulator: fuel pressure regulator was the issue.
Performed a intake pressure test and no leaks.
Car runs great.

Mods:
RMW tune, dominator cam, 440cc injectors, JCW head and pulley. 2% oversize ATI damper, obx header(with stock cat)
2006 R53 JCW

 

The problem is that most generic code readers can't clear the codes in a MINI. I had a similar issue with mine and an EVAP code. No matter how many times I had cleared it it would not go away. It only went away when I disassembled my car and had the battery out for a week. I would try disconnecting the negative terminal overnight or for 24 hours and see if that does it. Other than that, it is a trip to someone who has the right scan tool or the dealer to get it eliminated.

 

My info is there are 3 types of codes. Active which means the CEL is on, pending, and permanent.

In the case of permanent this can be an active code that had its problem addressed, the code cleared, but the automaker considers it "permanent" until there are so many warm up cycles with the problem/fault not detected and only then will the engine controller clear the permanent code.

It reads like you are encountering a permanent code. Different states have different emissions rules and maybe a permanent code might cause the car to fail emissions. You'll have to research this. If this is the case then you'll have to drive the car enough separate occasions to clear the permanent code.