I recently bought a 04, Z71 avalanche 60000 km on it. I started getting engine service light . I got it checked and the computer said it was running lean on bank 1 and O2 sensor, I put the good gas in and no change, I changed the manifold seals at a 200 price tag, and i checked the o2 sensor which is reading correcty, no leaks in the exhaust. no gas leaks at all. I'm S T U M P E D!!! I'm ready to actually got to the dealer, with my tail between my legs and my wallet wide open, help me before this happens PLEASE.:confused:

does it have any misfire codes also? what manifold seals...intake or exhaust? pull the spark plugs on bank 1. how do they look? is one of then kinda white looking, or all 4? post back what you find!

No there isn't any missfire codes, Intake manifold, the truck idles nice so I don't think there's a fowl plug, I'll pull them and check, The O2 code is gone now, just the running lean on bank one,

what was the exact code for the 02 sensor? it might be a plug that has bad gap setting, could be an injector clogged/faulty. the possibilities are high right now, and trying to narrow it down. a white spark plug end would mean lean on that cylinder, if on all 4, would mean something wrong on that side of fuel rail....either all 4 injectors bad at same time(doubtful and you would have other driveability concerns it would seem), or a clog in the rail on that side, or some sort of electrical problem over there. awaiting more info about the plugs. just for record, how does the truck run, any performance issues, or just the light?

I don't remember the o2 code, I have not had time to check the plugs yet, and it runs great, idles good, a few hours ago I switched the o2 sensors to see if the running lean on bank 1 would switch sides to eliminate the o2 sensors, then I,m to check the plugs, I doudt it would be a plug because then I think it would be running rich in the exhaust ? , but could be.


I just hate that light:banghead:
thank you, your comments are very helpful

Fuel pressure or MAF sensor or vacuum leak can give lean running codes.
MT

My truck was setting lean codes on both banks. After a few days of research and multiple resets, I decided to open the hood and take a look. The air intake tube between the air filter housing and the engine was disconnected. I reconected it and reset the codes. The code never came back. I know it sound like BS, but it really was causing the lean codes.

check fuel injector o-rings for leaks on bank 1,while running,spray brake clean around injectors or check for vacuum leak somewhere else if engine rpm changes,you most likely found your leak

check fuel injector o-rings for leaks on bank 1,while running,spray brake clean around injectors or check for vacuum leak somewhere else if engine rpm changes,you most likely found your leak

Good info, but please check the dates before posting, this is over 1 and 1/2 years old and inactive, thanks.