I keep getting the freaking code system too lean bank 2. I have replaced maf, pcv valve, intake manifold gaskets. Carbon cleaned 10k miles ago. Replaced downstream 02 sensor because i haf a code for that too and went away. What the hell i'm i missing here? Does the intake manifold fail? Is there any hose that goes bad and causes air leaks? Car has 200k miles and drives fine with no symptoms. Just that freaking code.

 

you need to closely inspect all vacuum lines for leaks. there could be a rip in the intake airbox tube.

- Downstream vacuum leaks of the Mass Air Flow sensor
-faulty or cracked PCV line
-fuel injector(s)
-exhaust leak
-possibly weak fuel pump or clogged fuel filter

 

I think i will take it to dealer for them to diagnose it

 

For the life of you don't go to the dealership.

Do yourself a huge favour and find a reputable mechanic nearby to diagnose it.

 

I rather pay the $80 for the dealer then a shop that will guess and charge me $60

 

Well, the O2 sensor in the driver's header is telling the ECU that that head is getting more air than the RHS head. It could actually be, from a faulty/missing gasket between the head/lower/upper intakes, maybe even a somewhat loose fastener. It could also be getting more air from one of the vacuum hoses being cracked, a couple of mine have duct tape on them for this reason.

One of the O2 sensors in the headers could also have gotten sooted up pretty good from the decarb process. Pull them out and--someone stop my first instinct if it's wrong here--hose them with some throttle body cleaner and towel dry.

The too lean condition could also be caused by the LHS head's injectors not operating as expected from a loose/shorted wire. With the intake off, inspect the injector looms from the injectors themselves all the way to the injector driver bolted to the front RHS of the engine, maybe a wire got pinched.

Edit: pop off the plastic intake and look at the butterflies in your SCV manifold (the brass plates screwed to the rods going through your ports). If both sets of butterflies aren't mostly even, then one bank of cylinders could be starving for air and kicking the dummy light. Albeit, the SCV motor is on one shaft, and the sensor is on the other, and I'm pretty sure it'd pick up on an angle mismatch, but if there's something else going on...like some FOD...

Edit2: just thought of a really bad scenario: RHS cylinder head spit a rocker out. Pulling the valve cover is the only way I know to inspect for that. Be wary of all seals upon reassembly. Definitely exhaust other options before this, since VVTi oil pressure is run through the valve cover.

Edit3: nevermind, I'm dumb. You can check to see all the valves are opening and closing with just the intake off and spark plugs out. IIRC, the crank snout is 24 or 27mm socket. 24 sounds more correct to me. Bar the engine over and observe the valves...stuck valve=head comes apart so you can put the rocker back on it's valve. Exhaust valves will need the headers off and a borescope.