I am getting an engine fault light in my Vauxhall Corsa 2011 with fault code
P0171 "System too lean"
This is not constantly on and only comes on intermittently. This caused a problem when taking it to my local garage because they could not diagnose the fault as the light had gone off. The light came back on after an hour or so of driving.
Does anyone know what this issue could be? There are a number of possible reasons listed online but I didn't notice anyone saying it comes on intermittently so this may be a clue.