Lean codes bank 1 and 2. 2003 Sienna

Updated, Checked every vacuum hose. Tried propane tank again. I finally read about smoke machine. I used to have a Party fog machine. That I think would have worked. I spent some time in Toyotanation readinG. Some ideas. ECU, My after market AF O2s, One guy wrapped plastic shopping bags around his big air cleaner clamp fittings an found leaks in plastic airbox . Check grounds. Something about coolant temp fauge

Do you have freeze frame data for these codes??

Yes, I cleared them when I reset the CEL. It should trigger again today and I’ll grab it.
I read about using a cigar And tubing to make a smoke machine. I’m going to give Myself and the Sienna lung cancer later today.

Here is today’s cel. Freeze frame. Mike

This freeze frame data is for the P0174, the P0171 did not return?

This freeze frame data is going to change your diagnostic approach because it is now a bank-specific problem. So MAF, MAP, Fuel PUMP & Pressure can be eliminated as a suspect.

What can be suspect is B2S1 O2 is 'lying', reporting a lean condition when there isn't one.

Air entering the exhaust system ahead of B2S1 02

Internal Vacuum leak on Bank 2 ( there should be no vacuum present in the crankcase when it is isolated from the PCV system)

Or, all three injectors are actually lean on Bank 2.

Please post again your Fuel Trim Data at idle, and at high rpm for both banks.

P0171 has been the code 95%. Of the time. I have got both codes when I was pulling hoses while checking around. So yes that is different to get p0174. On Pcv pressures. This engine has a 1/2 inch hose going from valve cover to intake snorkel. See picture. Note I wrapped a shopping bag to see if it would vacuum in .

The trim picture is 1000 rpm. Then 2000. Then 2900. The pink line shows the TPS %

Thanks for the new ideas.

I'd like to see the air/fuel ratio data for bank 2 and compare it with bank 1 which is OK. The A/F ratio data is given in a voltage often called Lambda with 3.3v being stoichiometric. Anything above 3.3v is lean and anything above 3.3v is rich. Does that voltage vary when you snap the throttle? How does it compare with bank 2 voltage? There is also an equivalence ratio that should be around 1.0 with anything above being lean and anything below being rich.

Are the upstream sensors able to be swapped? Could you move B2S1 into B1S1 location? I think you said you replaced the sensors. What brand sensors did you use?

Revision. Although the freeze frame listed p0174. When I went to clear it, that screen listed codes for both banks.

You would check for vacuum in the crankcase at the oil dip tube with the PVC plugged and isolated.

Is it possible to show the data on your phone app as just numbers and no graphing?

These graphs aren't relevant to making a diagnostic decision.

Weycraze, Enclosed is a data file. It was a CSV that I imported into excel. The data is recorded by the second the ecu read it.
I will check the crankcase pressure today. Are you interested in crankcase pressure to see if my rings are bad ?

Data file . Mike

John Clark,

I did buy Cheaper O2 sensors. They are both the same brand. I am considering your switch the O2's idea.

The bank 1 O2 was harder to change. I am pondering if I want to hang over the engine for an hour today.
This engine is the Toyota version of a Slant 6. Slant V6. Bank 2 is vertical and Bank 1 is at 2 o'clock toward firewall
You have to remove the intake manifold to change those 3 spark plugs.

Side note: I drove this for years with the O2's having failed heaters. It drove fine. I think it was open loop the whole time. I had thought the O2's would just take longer to heat up to start working. I think I was incorrect on this.

Reading voltages. My reader data only shows voltage value O2 sensors . there should be 2.

here is what is available.
Oxygen sensor 1 Wide Range Equivalence ratio 11.989
Oxygen sensor 1 Wide Range Voltage 2
Oxygen sensor 2 Bank 1 Voltage 0.15
Oxygen sensor 5 Wide Range Equivalence ratio 18.611
Oxygen sensor 5 Wide Range Voltage 3.191

Maybe sensor 5 is not mapped correctly. Could Sensor 1 = Bank1 , sensor 5 = bank 2?

Oxygen sensor 2 Bank 1 Voltage 0.15 What sensor is this. It says Bank 1, why don't I have a Bank 2 voltage PID?

FYI , I uploaded a data file in a post today

Thanks for your interest and help! Mike

Many engines do not do well with the wrong O2 sensors in them, especially engines using air/fuel ratio sensors in the upstream positions, like this one. I would ONLY put Denso O2 sensors in these. That's what came in them and that's what should go back in them. If you put some other cheap brand O2 sensor in that could very well be the issue. I've seen that many times.

Additionally, air/fuel ratio sensors have to be much hotter than traditional narrow band O2 sensors in order to work. If the heater fails in an air/fuel ratio sensor it will never warm up enough to work. If you drove for a long period like this then there's a good possibility that when everything is fixed you will have catalytic converter failures.

I looked through your data and while it's hard to analyze that data with no references as to what the vehicle is doing, other than RPM in there, some things I noted were very rich and very lean air/fuel ratio sensor voltages. I'm not sure what the bank 5 is but it shows it as an air/fuel ratio sensor voltage so it makes me wonder if that's really bank 2 air/fuel ratio sensor. 3.3v is the normal voltage for a Toyota air/fuel ratio sensor when the mixture is at stoichiometric. Higher voltage is lean, and lower voltage is rich.

Going cheap on an O2 sensor is never a good idea. If there is anything in there but a Denso sensor I'd change them out before going any further. RockAuto usually has the best deal on the Denso sensors if you have time to wait and are on a budget. Amazon and eBay parts can often be fakes. If time is critical have your local parts store get you the proper fitting Denso sensor. Don't use the universals, either.

Yes, I've read a bit about only use Denso A/F. The number on the O2 does pull up Denso product but I sure its a knock off. I'm out $35 for the pair. I'll order one Denso, just to see if it fixes one bank.

I also think the O2 labels are off in my scanner App.

A Denso upstream sensor for this car is $115 even on RockAuto and that is the least expensive upstream sensor they have. The NTK sensors, also very good sensors that I would use if a Denso wasn't available, are more expensive. Most of the time you can go Denso or NTK without any trouble on any vehicle that came with one or the other. However, if you picked one up for $35 it's not a Denso air/fuel ratio sensor. There's no telling even what it is. If you're going to order from RockAuto, I'd just order them both. You don't want those $35 sensors in there. If your converters weren't cooked already they will be after using something like that.

Another thing to consider, many of these engines that use air/fuel ratio sensors for upstream will use the downstream O2 sensor data to supplement fuel control. Generally, with standard narrow band sensors for the upstream, the downstream sensor is just for catalytic converter checking but air/fuel ratio sensor cars often use that downstream for fuel control, as well. Don't go cheap on those either or you can have issues, as well.

Yikes, $120 per O2 AF for Denso! Any other brands good?

Not if you want the car to run right.

Denso is actually the cheapest Rockauto offers.

Remember, the O2 is the heart of the fuel control strategy the computer uses to run the engine. Garbage in, garbage out.

There's no point going further here until you change out whatever junk you put in for air fuel ratio sensors.

Unfortunately, I can't do anything with this data set...did you have the option to export the file as comma delimited?

I can't re-arrange the data set because the times would wrong. Also, the labelling of the Oxygen Sensors can be misleading.

The fuel trims IMPROVE at higher engine rpm both banks, still suggesting a vacuum leak.

If the Wideband O2's are telling the truth, when you add propane into the air tract at idle, the LTFT should start to Improve. IF they do, I would still be leaning towards the vacuum leak.

If the LTFT's don't improve or the wide bands don't respond to the Propane enrichment then clearly there is an 02 issue.

Waycraze, The comma data is just like the excel data. A record for every data point. Not cool. I will feed propane into the intake and post results.

I stuck the old sensor o2 back in to see what it reads. It only shows ltft. See attach. The new and old both read about the same ltft. Kind of makes me think the new o2 is accurate. Wishful thinking probably

Updated, Checked every vacuum hose. Tried propane tank again. I finally read about smoke machine. I used to have a Party fog machine. That I think would have worked. I spent some time in Toyotanation readinG. Some ideas. ECU, My after market AF O2s, One guy wrapped plastic shopping bags around his big air cleaner clamp fittings an found leaks in plastic airbox . Check grounds. Something about coolant temp fauge