if it is ust an oil level issue or voltage problem, it should clear itself, but a log of the fault will retain in its memory, but be out of limp mode.
If the fault is more serious i.e. not voltage or oil level related, diagnostics is needed to see what the problem is...
All we are doing here is giving you the initial checks, P38's (well any Range Rover) absolutely hates low voltages, it causes all sorts of weirdness that will lead you to chase your tail all day trying to fix it....
First check with any fault is battery condition and voltage output...that will eliminate most things....
once that has been established and corrected, move on to the next fault finding items...
So, you seem to have low Alternator output and a small battery, sort these first as these will not help any further diagnostics...
Fit the largest battery you can squeeze in there...as Alan says, come winter you'll be pleased you did....P38's, cold weather and weak batteries....bad news!
