Unsolvable P0171 'System Too Lean' Code

fingers crossed for sure, but I'm going to save the dancing until t-minus one week from tonight, lol.

At the very least, they fixed an issue with my supercharger that I didn't know I had, so that's cool!

 

Here's what my service diagnosis says:

"Live data showing lean condition is active. AF and O2 sensors are responding normally. Removed MAF sensor for inspection and no problem found with sensor or pin fit. Test drove vehicle and under normal driving conditions and vehicle's fuel trim is normal. Lean condition only occurs at idle indicating possible vacuum leak. During inspection found exposed port on back of supercharger causing vacuum leak. Supercharger installation shows port plugged. Plugged port and fuel trim dropped to normal range. Cleared codes."

Sounds pretty thorough to me, but how can they tell there's a difference between my truck's fuel trim at idle versus while driving

 

They had the TechStream program computer plugged in and went for a drive. Recorded live data doing this.

 

Oh cool, wasn't aware they could do that, that helps me feel better about their diagnosis, thanks

 

weren't some equipped with EGR access for the 4Runners? could be whatever they used to plug the port didn't hold or was just rubber that dried up and cracked

 

Not sure, I was a little curious about what that unused port was there for. I assumed it was for certain rigs or models. Either way, I'm glad they fixed it because I definitely notice better performance from the s/c now. Just hoping that was what was tripping the lean code, everything's still good today.

 

Eon, did you see that new thread today where a fella slapped on a charger and has the lean code too? He's gearin up for fuel mods it looks like...

We've already kinda hit on this a lil bit but it seems even though the charger isn't posed to need anything else to run properly most peeps at lower elevations end up needing fuel mods of some sort to avoid a lean condition. Where as high elevation guys seem to get away with it pretty well if they want to. Even then alot of guys still do mods of some sort/degree.

 

I haven't seen the thread yet but I'll definitely look for it tonight when I get home, thanks for the heads up!

Yeah, if my problem persists even after all this I'll need to look into upgrading to the URD 7th injector. My only concern with that is that it's not CA legal smog-wise, it'll fail the visual inspection (assuming the inspector recognizes it). From what I've read from other CA guys, its sort of hit or miss if you get busted for it or not. Either way, if I have to go that route I'll cross that bridge when I have to lol.

I'll check out the other guy's thread, 'cause he might have a loose or uncapped port on his s/c as well that's causing the lean out, at least that's supposedly what happened with mine. Time will tell

 

I have no idea why I didn't think to do this sooner. I've searched these forums high and low since having this problem, but I never thought to search the keywords, 'supercharger P0171'.

Turns out, there are several threads like this one:
https://www.tacomaworld.com/threads/cel-p0171-after-trd-supercharger-3-4l.247252/

...and all of them found an unplugged port on their supercharger that caused the code. Now I feel dumb

 

Update: It's been exactly one week since Toyota capped the exposed port on the back of my supercharger and the CEL light has stayed off, no more P0171 code. I am resting much easier now...assuming I didn't just jinx myself

In case anyone comes across this thread in a search with similar issues (and you don't want to read thru 7 pages of frustration lol), if you've got a P0171 code the most common culprit is a dirty MAF. Clean it, if that doesn't help then it is most likely a hidden vacuum leak. If you have a supercharger, check the ports on the back; Tacomas don't use one of them and it should be capped, apparently it's not that uncommon for it to come off. There are plenty of other reasons for the code (exhaust leak, clogged injectors, bad o2 sensor, bad cats, etc.) but they're less likely.

Now I just need to get around to changing my fuel filter and I'll be golden

 

What's the hurry? My last Tacoma went 300k on the original filter.

Just kidding here. Baby that thing and get it changed.

 

The service techs told me it was in need of changing when I picked her up last week....I thought it was a little weird they didn't just change it or offer to, considering it could lead to the very problem I was having in the first place (running lean). But it seems like an easy enough task to take on myself.

Not sure why it is bad on a truck with only 25k miles on it, but I assume that it's likely because the truck sat for long periods of time without being run and that may have caused issues with the gas quality and fuel filter.

 

Its not. Its called up selling.

 

Lol, go to one dealership and they'll tell you that it needs to be changed at 25k miles, go to another and they'll say it's a "lifetime part". I changed mine at 160k. You'll be fine. Just run some Chevron concentrate through the fuel system every now and then.

 

yeah you guys are probably right, honestly if my fuel filter was that bad I feel like there'd be signs and she runs/drives like a dream ever since they fixed the vacuum leak. Just in case I'll pick up a Wix fuel filter just to have one since they're cheap, if/when I find I need to change it out I'll just do it myself. Thanks for the input

 

Pick up a factory one IMO.