Engine light on, rumbling in truck

[maegpie14]

I have a 2008 chevy Colorado and about 2 months ago my engine light came on. Code came up as fuel system to lean- bank 1. Made sure my gas cap was on, cleaned my sensors and also got my O2 sensors changed. Light is still on but truck ran just as normal so I decided not to follow through with it. (couldn't really afford it). a couple weeks ago I had to use 4x4, put it into 4 high and my truck started rumbling REALLY bad. Couldn't even go 10 km. So I switched it into 4 low thinking maybe it was just stuck as I hadn't used it in almost a year. 4 low was even worse - as soon as I stepped on the gas the truck jerked and it seemed like it was taking alot for it just to get up to 5 km. Switched back into 2 wheel (Note: I did stop and out it in neutral each time) and it drove a bit better but around 40-60 km it starts rumbling (not as bad but still there) as well as highway speed (110 km). Now recently, the last couple days, I've noticed to jerks every time I press on the gas to accelerate (from 0 km). Any ideas? Not sure if the engine light has anything to do with it but I thought I would throw that in there just in case.

[newdude]

Have it scanned for codes as soon as you can. Autozone does it for free if you can get to one. The light being on with rough running, its on for a reason. Something is up. If you get a chance to have it scanned, post the codes here too.

[maegpie14]

I have an engine scanner at home, will do it as soon as I'm off work tonight.

[maegpie14]

Code that came was P0171 - System too lean.

 

Took my truck to a family friend who used to be GMC mechanic (now retired).

He said its the transfer case (the rumble) as well fuel pump (engine light problem)