Lean codes 171 and 174 driving me nuts

Basic info and symptoms: 2008 Tundra 5.7 150,000 miles. The usual symptoms ie; CEL (on) VSC (on) 4lo (flashing) traction control (on) and lean codes bank 1 and 2.

Basic checks: MAF sensor spotless, cleaned anyway no change, lights up after awhile. Replaced MAF, same crap. searched/tested for vacuum leaks, none found, hoses like new. Idle rpms to spec, manifold pressure at idle 21 inches, applied brakes still 21 inches, rock steady.

Not ruled out but not likely issues: Fuel pump/fuel filter (no performance issues under load or heavy acceleration) o2 sensors simultaneous failure? (when was the last time you were dealt two royal flushes in a row) AIP, hmmmm2 of those also plugged in separately. AIP bypass relay two of those also. ECU? Expensive for a maybe.

Notable: Only seems to occur at low speeds or stop and go, never at highway speeds, absolutely no performance issues except possibly in town mileage reduction hard to tell.

Question for Mr. Toyota, if I have a lean condition why light up the whole damn Christmas Tree with seemingly unrelated lights? Bad design? Other? Splain me Lucy!

Does anyone here have an idea or see major flaws in my deductions?

 

At 150k I'd give it all new Denso O2 sensors just to rule them out.

The VSC and traction lights I'd say are probably a flaky wheel speed sensor. A good scanner should be able to show which one is acting up

 

What is your fuel trims?

 

The other lights come on to let you know that those other systems have been disabled due to the CEL. People tend to ignore just a CEL, light up the entire dash and they panic and get shit fixed.

 

My wife's 4runner showed it was running lean on both banks. Woman at O'Reilly's told me my cats were bad. Went to autozone, old man read the codes and asked when the last time I changed the air filter was. It was filthy easy fix. Felt like an idiot because I never changed it.

 

Given its both codes, needs to be something upstream of both sides… cause I doubt it’s both oxygen sensors. Maybe replace intake gaskets? They should be cheaper than MAF.

 

Thanks people, tomorrow I will change the upstream o2s as I already have them. As for the flaky wheel sensor theory, nah only shows up with lean condition never independently but will check anyway. As for dirty air filter and MAF both have been replaced recently and I would expect a dirty/plugged air filter to result in a rich condition. Seems a vacuum leak would hang around all the time and result in triggering alarms every time you started it up. If a lean engine condition deliberately shuts off VSC and traction control unnecessarily I can see a big lawsuit. For instance I just left work and a blinding snowstorm is raging and road is iced, uhoh lean condition and traction controls fail by design and I slip into the path of an oncoming snowplow because of it. I'm suing big time because that was a STUPID DANGEROUS idea. Next time the lights go ape I will determine if they are truly disabled or if it's just the lights. So let's keep this going until problem is resolved and maybe save someone else a headache and unnecessary expense. I will also check fuel trims. Afterthought, could a wheel speed sensor fault result in a lean code? Toyota could have made this much easier to diagnose, Why didn't they?
3 smoke tests, nada, pressure test @ 5 psi, sound and bubbles, nada. fuel trims did indicate lean condition. OBD II tester faulty? Truck up to temp and idling, deliberately pulled a vacuum line and let'er suck 15 minutes and no codes. wtf?
ECU/ECM? Next, even though no performance issues, I will be checking fuel pressure and volume. I was able to engage 4hi, didn't try 4lo.
Fuel checks, NORMAL, upstream/downstream o2 sensor readings, NORMAL!

 

Charcoal canister cracked from uneven roads and cold temps? Snacking rodents? Any droppings under IM (will a flashlight and mirrors) or debris from them? Fuel filter is an easy swap too...swap some vacuum lines as it's easy, and once "warm" could seal back somewhat to not leak enough for errors if it is a vaccum issue..just spit-balling ideas....