Any suggestions on where to start looking for the culprit of a P0172 & P0175 (Bank 1 & Bank 2 too rich) codes?
2010 XFR with ~105k miles on it now (love driving this car).

The other night when I was driving, about 40mph, was in S" and locked in a higher gear (4 or 5 if I recall), gave it some gas and it started "hiccupping/pulsing" for a moment. Weird. Clicked into 3rd gear, and it pulled away just fine. No DTC light at this point. Ran just fine the rest of the day. Next day, similar situation (slower speed, higher gear, more load), and it "hiccup/pulsed", drop to lower gear, and it smoothed out, but the DTC light came on. Drove it all day yesterday without issue with the light on, hoping it would reset on it's own (no symptoms all day, and fuel econ seemed normal). I was thinking it was a lose gas cap or something stupid. I got home and pulled the codes above.

O2 sensors seem to be cycling fine when I hooked up the computer to scan it. I cleaned out both air boxes (nothing much in there) and the (OE paper) filters are both good. Removed the right and left MAF sensors (post air filter on the air intakes) and sprayed them down with MAF cleaner and reinstalled.
Reset the DTC. This morning it drove fine (seemed really peppy actually). Then the DTC light came on again as I was pulling out of the carwash. Continued to dive to work, doesn't feel much different, no pulse/hiccups, but the light is on again. I'm assuming it's going to be the same when I get home to pull the codes this evening.

Not sure where to look next? I doubt it's the O2 sensors (why would both banks die at the same time), so I'm thinking TMAP sensor (not sure where it's located), or some sort of air or vacuum leak post sensors? Wouldn't a bad TMAP, MAF, or injector have a different or more specific code?

There were no misfires indicated current or stored, so that's positive I suppose. Wouldn't think a random leak would happen, but I suppose the cold weather is making things contract or brittle.
Any suggestions on where to look would be appreciated before I send it over to my mechanic. This has been a great car and this is the first "serious" issue I've had with it aside from the water pump replacement that everyone does.

Thanks in advance!!

 

I rather suspect the main O2s are the front ones and they don't/shouldn't cycle...

Something sounds seriously wrong.

It's a very complex car and guessing/hoping may be a disaster / very expensive.

 

I'm wondering if I was looking at the wrong data log/graph for the o2 sensors it was an unfamiliar scan tool program...Regardless, I appreciate the response.
It will most likely go to the mechanic.
I have the Mercedes STAR Diagnostic multiplexer and software, but I haven't yet obtained the corresponding JLR VCM system...Haven't needed it until now. LOL. Frustrating flying blind on this vehicle. I like to at least have an idea what's going on before dropping it off (or the ability to bring him the parts).

 

Well for what it's worth...Called the mechanic. He was swamped so we set an appointment the following week to have him look at it. Decided that since it seemed to be driving fine that I'd continue doing so. Put about 300 miles on it, and the check engine light turned off on it's own a couple days ago. No issues since. No idea what could have triggered it as there were no other codes pending. Just the 0172 & 0175 stored that didn't point to anything else. Going to keep an eye out on it and chalk it up to a temperamental sensor somewhere.

 

Found some sensors to look at here, and don't forget to make sure that battery is up to snuff.
https://repairpal.com/OBD-II-Code-P0172-and-P0175

 

A diagram of a general OBD II car:
OnBoardDiagnostics.com - Engine Basics

All the sensors & actuators need to work properly. Can't emphasise "all" and "properly" enough. Expect codes if not.