Mystery check engine light on 2010 Rav4

[kissinger]

I’ve had a couple of check engine/ABS lights come on recently. First time my mechanic couldn’t do anything because the fault disappeared after I turned the engine off. Second time I managed to get it there without having to turn engine off. He scanned it and said it directed to a fuel injector (bank 1) issue, but when he checked it out he said the injector in question was fine. The car also drives fine. 
 

He said it could be being caused by poor quality supermarket fuel and that if I ran it dry and then refilled with good quality fuel there’s a good chance that will fix it. 
 

Have any of you guys had a similar problem in the past? Which fuel would you guys recommend (BP, She’ll, Essie, etc)? Are there any other products it’s worth trying (Redex, etc)? And would it benefit from a bit of an ‘Italian tune up’ on the motorway?