P0172 code Rich Fuel Bank 1 2012 Prius V Wagon 196,000 miles.

My 2012 Prius V wagon shot a P0172 code = rich fuel bank 1. I took out and cleaned the MAF with CRC MAF solvent. Let dry a few hours and screwed back in. Also bought new Fram Ultra engine air filter at Walmart and installed.

Next is a whole plethora of things it could be. This is said to be the most difficult code, since it could be so many issues. I'm thinking next to try to do the coolant temperature censor, the upbank, or upstream, O2 sensor, which I can likely access by taking off the windshield wiper motor, and the dummy/blocking plate, with those fifty nuts, below that. Once you remove that hands blocking, black, steel, plate it's pretty much Shangri La in terms of access to so many things. It's the one you gotta remove to do coils/plugs. I did find two nifty plastic clips, which can be done by hand, however, to add DOT 3 brake fluid.

Anyone ever shot a P0172 rich fuel bank 1 code? What was the repair that got your check engine light to finally go away after shooting that code?

Here are some troubleshooting suggestions I found online:

1. Clean MAF and O2 Sensors, Or replace. Cleaned the MAF with CRC, already.
2. Replace spark plugs(already did all plugs And all coils due to different code before this one).
3.Replace coolant temperature sensor. Question. Do I have to drain coolant to replace it?
4.Repairing vacuum leaks. Question. I called AutoZone and a guy told me to start with intake gasket.
5.Replace damaged fuel regulator, fuel pump, or fuel injector. Like, where in the world are those?
6.Replacing restricted air filter. Done! Put in top of the line, Ultra Fram new air filter.

Here are some possible causes for tripping P0172:

1. Faulty O2 sensor, or oxygen sensor.
2. Dirty MAF sensor. I just cleaned and put it back in. Maybe need a totally new one?
3.Damaged fuel line.
4. Defective fuel pressure regulator. Where in the world is this thing located?
5. Damaged, stuck open, thermostat. Yuck! More coolant stuff.
6. Faulty plugs. I've changed them all, TWICE, already. And their expensive coil on plug coils, too.
7.Clogged/dirty air filter. Just changed this yesterday evening with the best filter.
8. Defective fuel injectors that leak into combustion chamber. No foggy clue where injectors are.
9.Faulty MAP(Manifold Absolute Pressure) sensor.
10.Damaged throttle position sensor.

I'm just at a loss to know 'which one' of all these it could be. That's why I'm reaching out for help, to hear from those of you who've gotten the same code, 'P0172,' or have known people, or worked on cars, that also have gotten that code. What was the thing that resolved it for you?

I was ready to start ordering an O2 sensor, and possibly a coolant temperature sensor, online, but wanted to get others' perspectives, or hear their own experiences, with this particular code, first, since they say it can be so many things. Is there something, or a set of things, that it has a much greater probability to be? Help!

Finally, I got this code with my hand held, O'Reiley Auto Parts purchased, OBD II reader. The Toyota dealer has told me their laptop diagnostic cost is 109.00. Is the dealer's diagnostic service better than my handheld OBD II code? Maybe their technicians have seen P0172 before in Priuses, and they retrace their footsteps the last time they resolved the code, whether for their own hybrids, or their customers?

I'm really tempted to just throw down the money for the upbank O2, and the coolant temp sensor, and just start doing anything, but I don't want to do multiple, possibly unecessary, repairs, since I'm at almost 200k miles, this is my only vehicle, and I'm not rich.

I've also read online that you can drive on this code, but that it could later affect the catalytic convertor, or possibly other parts. I'm noticing no symptoms right now, but the check engine light still remains with the same P0172 code, even after cleaning the MAF and replacing with brand new, top of the line, Fram Ultra air filter.