P0138/0158 After starter job, unsure where else to look

Easy option would be vacuum leak. Well I've got not a damn clue where to look so here's some info. Long read so be warned, I give a lotta detail generally.

Very technical person so interested in what options you guys would have to troubleshoot. My current problem is as such.

06 2uz tundra. Did starter job recently after it went out, after hooking everything back up and starting it everything seemed fine, no issues at all. After enough driving for a two trip detection cycle, it threw P0138 and P0158, the former of which coming with freeze frame data. Nothing particular seemed out of whack except I noticed the obviously high voltage of the downstream o2's, and decently high positive LTFT on both banks, but primarily bank 1 at ~14% and bank 2 ~6% at a steady cruise at 1600rpm.

I figured, ah vacuum leak prob closer to bank 1 side. Grabbed the smoke tester, no smoke leaking anywhere. Okay, maybe that's not enough or it's not happening under positive pressure, odd, lemme try carb cleaner around all the sealing surfaces and vacuum hoses besides the ones under the rear of the manifold ofc. Nothing. No surges, no sputtering, car doesn't even run bad. Tried a vacuum gauge, close to 22/23 inches of mercury and needle was dead steady. Only weird thing was when I created an artificial vacuum leak using the SAIS VSV's, I felt vacuum from the source that comes under the manifold, but it didn't affect how the car ran. I pulled the EVAP purge and PS idle up valve lines and it very clearly ran poorly for a second. Other than that nothing.

So can anyone tell me how by chance, my O2 sensors that are well grounded, bc I didn't remove any grounds when doing the job, are somehow both reading high while idling and most other driving conditions? I cleaned the MAF, compared the mass against normal values other owners get and I'm right in tune. It could be the O2 sensor's time, they're very old, but the odds are just low and I'd rather not drop $300 on 4 new sensors for a hail mary. Though the FSRM sure does think that's the best option for some reason.

Below is a list of parts btw for the starter job for anyone curious, this also includes basically every electrical connector under there bc odds are good if you're like me and have 330k + mileage, they're all brittle and need replacing.

17377-50010: Gasket for EGR stuff x 4

$11 22271-50050 Toyota Gasket - 22271-50050

22271-50050: Throttle body gasket x 1
17171-50030: Intake manifold gasket x 2
16341-50020: Rear Crossover pipe gasket x 2
17341-50180: EGR Related hose x 1
17342-50180: EGR Related hose x 1
89615-06010: Knock sensor x 2
28100-50101-84: Starter x 1
90980-11400: Starer Solenoid connector x 1
90980-11875: Knock sensor connector x 2
90980-10845: Main Air Control valve 3 pin x 1
90980-11149: Main Air Control valve 2 pin x 1
90980-11032: Air pump connector x 1
00272-SLLC2: Toyota Super long life coolant x 1 gal

 

Changing the front O2 sensors fixed my truck when I had those codes

 

Something just feels odd about just changing em out suddenly. Feels like it would have to be related to the maintenance somehow

 

Yeah, like a bad or loose ground, or pinched wire. The fact it's impacting both downstreams* and causing an over-volt situation is weird. Did you check the FSM for those codes and things to check? You can download a copy of the FSM around line 6 in the 1st reply of THIS THREAD (see 'Service Manual' link).

 

It seems to be affecting the downstreams, the upstreams are reading a relatively expected ~3.3V most of the time (bc the fuel trims clean up the problem after a few seconds upon detection), but the downstreams never fluctuates between .1 and .9 as expected, just stick around .85V and .95V respectively. When driving under certain conditions I can watch them go down to more expected values for a moment, but on normal driving they aren't acting right.

I checked the FSM and it has you replacing the heated O2 sensor two separate times before you even are mean to check the resistances between pins. Let alone check for shorts and otherwise. I'm just hoping someone has run into a situation like this before on this platform and might know of any gotchas besides just tossing money at O2 sensors.

 

Updated my reply, had a pre-coffee moment on the codes. But yeah, I see what you're saying about the DTC in FSM, 'Trouble Area' indicated.

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I think the key text is here, maybe not so much the "HINT", but the 2nd paragraph. You just had the "lid" (intake) off the top of the engine. It could suggest leak (if lean) or a fuel dump (if rich), knowing both the fuel lines and the intake manifold gaskets are potentially impacted by a starter job. While you can't easily check the gaskets, "rich" would be your issue here, so i'd be checking: Fuel rail connections, every fuel line joint is tight, all vacuum hoses attached to the fuel pressure regulator(s) are attached.

But I I'd also ask you this: At any point in this work, did you have the negative battery cable off for at least 10 minutes, forcing a re-learn? If not, can you try that, and see if the code returns within 20-30 miles of driving, after forcing re-learn?

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I did not do an idle relearn, I've had the battery off in the past and never came up to needing to. I gave it a shot and no dice, still same issue. I do have a question though, because something feels off with what I just found. Past the MAF in the air tube going to the throttle body, there are 3 air connections. One goes to the PS Idle up valve, one goes to the PCV, and one to the fuel regulator. If I disconnect any of those, there is no vacuum coming from the air tube. Is that expected? I can create vacuum leaks where the car struggles using any other sources of vacuum (besides the source for the VSV's for the Air control valves apparently, but that one definitely has vacuum). But even disconnecting the PCV, a massive hose, creates not a hiccup in the engine, or the slightest bit of vacuum while idling (highest vacuum load). Issue that comes up is that you mentioned the fuel pressure regulator, which doesn't actually seem to be getting vacuum at all when hooked up to the air box. I verified by looking at pages in the FSM that it's the correct place for the line, just feels very weird that there is no vacuum whatsoever. Mind checking on your vehicle what happens when you pull any of those 3 lines? Do you have vacuum coming from that resonator box in the air tube?

 

Turns out it only pulls vacuum pre throttle body when there's a throttle load. So that's fine, still in a weird place. Bank 1 still seems clearly leaner than Bank 2, ~15% ltft vs ~7%, haven't identified any clear issues yet. Could there be a problem with the SAIS system? Could that be leaking in a way that adds oxygen into both circuits? Maybe didn't tighten down the air control valves for each bank enough? Feels unlikely though. The exhaust smells rich so the ECU is overcorrected the fuel so I just feel like air is getting added somewhere, just not sure how I can test the exhaust for air coming in. Maybe a long hose or something, will try on next cold start after SAIS is done making a shit ton of noise.