Hoping someone can figure out what this issue is

Hi everyone,
I recently bought a 2006 V6 4Runner Sport Edition. There were a few lights on when I bought it and I'm hoping someone can tell me what it might be, or what I can check to see if I can diagnose the issue myself. Check Engine light is on as well as these lights:



The previous owner replaced the MAF sensor in January 2019, and a new catalytic converter put in within the last six months. The lights came on soon after this. He had the system reset, the lights stayed off for a while, and then recently they've come back on.

I checked for codes, and this is what I got:
P0174 System Too Lean (Bank 2)
P0174(pd) System Too Lean (Bank 2)

It idles at about 1100RPM.

Anyone have any ideas? Any suggestions would be greatly appreciated.

 

Don't know if you are still looking, but this suggests one of two things off the bat: your not getting enough fuel, or, your getting too much air, which could be triggering your O2 sensors (they are responsible, in part, for measuring the fuel/air ratio).

Since the MAF has been replaced, two other common things to check are for a vacuum leak (any extra or unaccounted for air getting into the lines after the MAF / Air Filter) and fuel line issues, e.g., fuel pump, fuel filter, fuel injectors.

I believe P0174 is typically the code for the Passenger Side UPSTREAM (before Catalytic Converter), and is more indicative of an air flow issue vice fuel issue (DOWNSTREAM O2 sensor is typically more fuel related, I think). These are not absolutes, just common generalities. However, it is entirely possible it is just a bad O2 sensor as well, which would give the false impression you have a vacuum leak or fuel supply issue. Again, it's likely Passenger Side -- UPSTREAM is the one in play here -- either it's bad, or it's accurately sensing something wrong with the Air/Fuel mixture...and more likely air.

Some quick (and cheap) options could be to clean the MAF with MAF Cleaner (I know it is newish, but can't hurt to clean it...they get dirty); change your air filter; or change your fuel filter (if it's not inside the tank) and see if those work.

There are several other possibilities, but those are some primary places to look (faulty PCV; failure in fuel injector, etc.). Good luck.

 

If you're getting those lights, but no code that seems to correlate to those lights (like say a wheel speed sensor or ABS code)... it's usually a sign that you need a zero point calibration done.

Either a dealership can do this; or there is a method to do it yourself using a jumper wire to temporarily short a couple of pins in the ODBII. I've done this in a taco before, but not a 4Runner. I would google 4Runner zero point calibration - it's pretty quick and easy to do; and worth trying, if even just to rule it out before going further down the troubleshooting rabbit hole.

 

I replace these part on my 06 and it fixed the problem.
https://www.amazon.com/gp/product/B00G0PQOJK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

Got a brake switch code which didn't seem to do anything except turn on CEL. Replaced it w/ Amazon Genuine Toyota switch (easily). Only thing different, CEL off.

 

On my 2007 Limited anytime the Check Engine Light comes on for any reason so does the whole VSAC series of lights.

Doesn't matter if it's throwing a code for an 02 sensor or a gas cap seal leak the dummy lights all seem to work in tandem.