I need help with this! The ENG Check Light on my 1997 4Runner has been turning on and off. The code that keeps coming back calls for "Bank 1 is too lean" The light in 97% of the times goes out on its own after a few days. This code does not really points to anything specific like a bad O2 sensor or clugged Cat Converter. At least to my knowledge. Has anybody had this happen before?

 

dirty connection or rusted out front O2 sensor ? possibly

 

use seafoam in every other tank for the next month or so.. and possibly clean your MAF... these trucks have a 3 trip detection and if it does not detect the issue in that time the light goes off... so this is an intermittent issue probably under heavy acceleration!! Clogged injectors and maf or front o2 sensor are likely to throw these codes
docktortal33has a valid point however!!!
Simply could need to run the seafoam and it will go away!!! Otherwise clean maf and check the front o2 sensor...usually when the maf is dirty and the ecm does not detect it it throws this code!!

Really should do all three!!!