P0171+P2195 lean on bank1 only

Hi Guys, First post here.

Here is my situation:
I purchased a second hand 2007 Tundra double cab long bed not too long ago but I did not drive it much.

It developed a problem with the secondary air injection pump, with P2440 code, bank 1 switching valve stuck open. After searching various Toyota forums, I DIY'ed a bypass kit using a regular automotive relay + 4.7k ohm resistor and some wires, and I also put in a bypass plate sandwiched between the switching valve and exhaust pipe.

The P2440 code went away! But I now get P2195+P0171 codes. I don't think I got these 2 codes before the bypass, but I did not drive the truck long to be really 100% for sure.

But in any case, regarding the P0171 and P2195 codes, here are my observations:
1. My LTFT and STFT for bank 1 are: ~30% and ~20% respectively,
2. LTFT and STFT for bank 2 are perfect, change between 0 and ~3%.

So **I think**, maybe my MAF and fuel system are good? Otherwise both banks will be lean, and I would get P0174 code?

I initially thought there is an exhaust leak on bank 1, due to the fact I took apart the SAIS switching valve on bank1, and I honestly did not see a gasket between the valve outlet flange and exhaust pipe flange, so I put on some Permatex Red High-Temperature RTV Gasket Maker between the switching valve flange and pipe flange and tightened them up good.

But after that, I still get P0171 and P2195 codes after 1 hour drive.

I then used Car Scanner app on my Android phone + ELM327 dongle to log AFR O2 voltages on B1S1 and B2S1, and during engine idling, I pressed the brake pedal to simulate a lean condition (this idea is from several Youtube videos).

My O2S5 voltage (Oxygen sensor 5 Wide Range Voltage, I don't know why the software shows sensor 5 voltage instead of sensor 2, but I assume this is the B2S1 AFR sensor, as other sensors are disabled in the software) consistently hovers over ~3.25v during idle, and goes up to 3.4V when I pressed the brake pedal, then goes down to ~3.1V when I release the brake pedal, then it will go back to ~3.25v after it "stabilizes" for several seconds.

My O2S1 voltage (Oxygen Sensor 1 Wide Range Voltage) however consistently hovers over 4.5V during idling, and it shoots up to ~5V after I press the brake pedal, it probably went over 5V as the software recorded a flat line at 5V for several seconds. Then the voltage drops to 4.5V, but it never went below 4.5V (like B2S1 does under 3.25v) and its response seems slower compared to B2S1.

I think my O2S5 (or B2S1) is behaving normal. But my O2S1 (B1S1) is not.

Are there other tests I can do to positively determine the problem is the bad B1S1? As I don't want to spend $180 dollars to replace a non broken AFR sensor.

I am thinking to swap the two AFR sensors from 2 banks, and observe the voltages and potentially trigger a P0174 code? If I get a P0174 after swapping the sensors, then I can positively identify the current B1S1 is broken?

What do you think?

Thanks!

Hexar

 

My old Mini VCI cable was not able to read Data List nor perform Active Test from TechStream, so I ordered an OpenPort 2.0 cable and it came this weekend.

So today I looked at several sensor readings and did a couple of active tests, including the so called "snap throttle" and Injection volume increase/decrease by 12.5% test from TechStream.

Here are some of the graphs recorded and my observations:

1) this is when I did a series of "snap throttle" tests: rev the engine to ~3000rpm, then release the throttle, then I blipped the throttle for several times.

LT Fuel Trim for S1 is 20%, and I think bank1 has trouble maintaining Lambda close to 1, and B1S1's voltage is consistently high, middle line at 4.2V and many times at 4.99V.

B2S1 seems to be much better.


2) This is another set of snap/throttle tests, and I was trying to observe both upstream and downstream sensors, trying to determine if my Cats are good or not.

B1S1 is again constant at 4.99V, and B2S1 seems normal.

I don't know how to read B1S2/B2S2 numbers, and understand their behaviors.




3) This is when I did several +- 12.5% injection volume tests for AF sensors from TechStream.

I was experimenting with Active Tests (first time) and observing the graph at the same time, so I don't remember how many times I tested and if I blipped the throttle in between the Active Tests or not.

But I can see B1S1 does not react to the injection volume up and down at all.

Odd is: fuel trim for both short term and long term came down to 0% for some reason? maybe communication problems?


4). This is when I decided I need to do exactly two volume up and two volume down Active Tests: +12.5%, -12.5%, +12.5%, -12.5%

It seems B1S1 reacts to the injection volume change, but not much? (the X time scale is short, and I adjusted Y axis range making the graph easier to read.)

And the B1S1 voltage is still very high, hover around 4.9V range, even the low readings are above 4.93V.



So what do you guys think? Is B1S1 bad for sure?

What other tests can I do?

Thanks!
Hex

 

I would recommend keeping it simple. Given that there is a possibility that the secondary air bypass that was just done could possibly have something to do with the new codes, I would advise to swap bank 1 & 2 upstream sensors like you had mentioned. If the lean condition transfers then you have enough proof to go ahead and replace that sensor, but I would start with that and go from there. Note: when fuel trims zero out or freeze its typically because the ECU is in open loop.

 

Thanks Josue914, I will try to swap the 2 upstream sensors next.

I am spraying PB Blasters every day.

 

My 30,000' view of this one feels like a vacuum leak. You have unmetered air in the system. Enough to mess with your trims but not enough to cause a running issue.
I read your posts but not in great depth. Just my two cents.

 

I thought about the vacuum leak, but it would not explain why bank 2 is running perfect. Your thought?

 

I can depend on where the leak is.
I had one on my daughter's car that was between the intake and the head. It really messed with on cylinder but since the system can only see a bank at a time with the O2, it will show up as a bank issue.
Not big enough to cause a misfire. But the system tries to trim out the fuel. You end up with three cylinders running a little rich and one running a little lean. The O2 can be fooled and see this as running good. But not totally.
Similar things can happen with small exhaust leaks. Maybe your fix did not seal off the old air injection port as well as you thought? Again, this is unmetered air in the system that the system can't account for. Not enough to cause a running issue but enough to throw your PCM into fits.
In my years of wrenching, I have dealt with very few bad intermitent sensors. Most of the time there is an underlying issue. This feels like unmetered air.

 

Thanks mverkaik, I will try smoke test the intake.

How do I test small leak for exhaust?

 

I took AF sensors off from both banks, they "look" ok and similar, with minor carbon buildup, I then "cleaned" the B1S1 with carb cleaner and ultra-sonic cleaned it with gas. I then swapped 2 sensors.

Now currently, on bank 2 (with old sensor from bank1) I got 20% short term fuel trim, and voltage is constant at 4.99v, lambda at >1.2 and I also have a pending code P2240 (Oxygen A/F sensor pumping current circuit/open (Bank 2 Sensor 1) )

Bank 1 behaves very good, lambda ~1.0.

So I guess, the AF sensor currently on bank2 is bad.

 

That does sound like you found your culprit. Nice work.
Keep us updated on what you learn.

 

Thanks mverkaik.

Here is an update. I think I fixed it.

I am the cheapest person I know haha, I have been procrastinating ordering a new Denso sensor from RockAuto, because of the ~$190 price + shipping. haha

A cheap person is almost always a packrat. I had a 2004 Sienna that I totaled in 2012, I sold most of parts I can take off from the Sienna, but no one wants to buy used O2 sensors, so I still have 4 of the O2 sensors from Sienna.

I started to wonder if they are any different from the Tundra's AF sensors. By the look of them, I found 2 Sienna sensors' "probe head" looks very much like the 2 Tundra AF sensors, so I think these 2 are AF sensors. Their parts number being 89467-08020/08010, my Tundra is 89467-04020.

So I started to google the differences between 08020/08010 vs 04020, like their specs, such as response time, voltage current etc., even though I would NOT understand any of these, I thought I could still compare the numbers. But Google AI did not tell much. I then figured, Toyota/Denso cannot design/produce too many different type of AF sensors with drastically different electronic specs, can they? The 2 cars are only 2 years apart, and they are all Toyota. I think writing software with different variables/default values etc. to suite different cars (such as displacement etc.) but with the same sensor hardware is much easier.

So I took off the bad B2S1 this evening, and found out its plug is very different from Sienna's. Left is Tundra's (04020) vs Right is Sienna's (08202/08010)

After panicked for a second, I started to wonder if I can swap the plugs. First I need to take the wires off the Sienna's, before I started, I marked the "sockets" with W for white, B for blue, and dots for the 2 black wires.


Then I took off the plastic "center divider", and I saw a tab near each of the four posts, and I found I can prey the tab away from the post


I can then pull the wire off the plug:


This is the wire, the plastic tab is holding the wire in by the middle "indent":


Once all 2 sensors' wires are all pulled, I then swapped the plugs, this is easy, just push the wire all the way in until you hear it clicks.

I then installed the hybrid sensor (Sienna's sensor probe/head with Tundra's plug) on to my Tundra as B2S1.

Started the truck and noticed lambda and voltage are all normal for B2S1, and truck went into CL super fast, almost like no time, maybe 10 seconds? In the past, it would not go into CL even after 10 minutes warming up, or before coolant temperature goes up to ~170F. STFT for bank 2 is around 0.




I tried several "snap throttle", and sensors from both banks reacted the same with very similar graphs.


Also Monitor for O2 Sensor is Pass even though Incomplete. In the past, this was the only monitor that fails.




So I am guessing, this issues probably is fixed. I guess Denso sensors, at least for similar year Toyota's, may have the same or similar electronic specs, different model numbers are just because different plug shapes and maybe different wire lengths also? I will see how long this hybrid sensor can last.

I will also see if my gas mileage will get lower, currently it is at 20L / 100km .

Cheers,

 

I don’t know too many people who would hang onto old O2 sensors

Thank you for the great write up and the lesson.