The light is back on after a week.. This time the system that checks the codes said it is lean bank 2. There are a few things this could be and one of the is a leaking head gasket, Not only will the antifreeze load up in the cylinder bust combustible gases will be detected in the radiator via a head test. The head test is a gadget they put on the radiator with a blue chemical and if it detects carbon dioxide in the antifreeze it turns green. My test did turn green however I do not experience a loss of antifreeze or any smoke in the exhaust and the truck runs great. About $800 to replace head gasket and I have no problem getting it done but the test seems a bit mid evil and until I have further proof I am going to wait. For now the mechanic gave me a bottle of a type of stop leak to see if it can help but if it comes in a can or bottle it is not a cure for what the real problem is. If any one can help, I could use some real world experiences.