Let me start with this is my first post here, I have been following this forum for a while now and you guys are great. I have fixed several problems with my Blazer with the info here.
My problem now is that I flushed my radiator, installed a new thermostat and cap and the next time I went on a trip the SES light came on

. The first code was 174 Bank 2 too lean. That one was cleared and then three weeks later the SES light comes back on and it now show 171 Bank 1 too lean.
Can any one tell me what is causing this?
97 Blazer 4dr 4X4 LS
124,000
Shadowstarr