Bank 1 running lean

[angusog]

Hello all, I've had an engine management warning light come up, mechanic pal had diagnostic on it and it's "bank 1 running lean". He couldn't find anything wrong so cleared the error and used it for a few days with no problems (all with my ok of course).
The error has come back now but the ex still seems to run ok. Andy (my mechanic pal) says he doesn't want to start throwing expensive sensors into it but can't diagnose the problem any further.

Anyone else had this error and found the cause?.
Any help greatly appreciated.

Thanks, Angus

 

[2000StreetRod]

Lean condition procedure

Lean condition procedure

 

[angusog]

Thanks StreetRod,
I've printed that and will get it to my pal Andy asap.
Much appreciated.
Your Helpful Threads section is great too.
I see you are in SC, I've been to NC a few times walking and fishing in the hills, great countryside. Too hot for a Scot in the summer though .
Thanks, Angus