Lean codes bank 1 and 2. 2003 Sienna

No change could be because it was leaking to the point it wasn't doing anything. What is your idle RPM with the engine up to temp and the AC off?

Matt, looks like my idle increase. To 900 with the throttle vac disconnected

John first pic is at idle. Second at 3000. Bank 2 is no behaving like 1

Check my high tech vacuum leak check. Two balloons over intake. Pressurize with bike pump. If I can inflate balloons, seems like I’ve plugged the leaks

Check your MAF. As a rule of thumb, at idle it the MAF reading in g/s should somewhat match the displacement of the engine. For example, a 3.3L V6 engine should have roughly 3.3g/s of air flow. It's not precise but should be somewhere in that range. Again, these snapshots of random numbers of data are difficult to analyze but I see some data captures where the MAF number doesn't seem like it makes sense for the RPM of the engine. I don't know the strategy on this older Toyota but you could try unplugging the MAF and see what different that makes.

Seems to me it takes something very out of whack to generate a plus 50% long term fuel trim number. I'm still VERY suspect of those $35 A/F ratio sensors. It wouldn't surprise me if both are skewed and one is not working correctly at all.

Can't really ballpark the MAF at idle because it's idling way higher than it should be. Guessing the idle should be somewhere around 600 rpm AC off not 900+.

Above he posted a spreadsheet of data called 05 30.xls. The first 11 data captures show idle speeds around 700 rpm. The MAF in those captures is around 4.2 at the 696 rpm, with around 5.5g/s being the highest at 747 rpm. Again, it's hard to analyze a spreadsheet of data like that because we don't know the data transfer rate and if any of the PIDs are lagging indicators of something that happened a second or two prior, but that is 11 captures and a significantly higher than normal MAF.

I also noticed that in data row 243 we have an RPM of 1429 and a MAF of 4.53 which equals the same MAF we had at lower RPM around 700-750

Also, in row 257 we have an rpm of 714 with a MAF of 2.75. It just seems very erratic to me but again it could be in the way all this data is lumped together.

The last 2 pics you posted with idle the air fuel ratio is 14.96:1 then at 3136 rpm you go to 17.07:1 so I’m kinda leaning away from vacuum leaks. Have you checked fuel quality?? Also can you give us a volumetric efficiency test?? We need engine rpm maf g/s intake air temp along with baro reading. Do a wide open throttle through first gear and give us those numbers. We want 80% or more. We need peak maf and rpm if your scanner records that

That test will rule out maf or say it’s dirty needs cleaned or replaced

There may be multiple issues here, underreporting MAF combined with a problem with B2S1 wideband. I only made 2 charts of the STFT vs Respective Wideband. Overall per RPM range, the MAF number seems very low.

I haven't seen what is displayed on Bank 2 when a Wideband goes to bias 3.3 Volts, but the PCM puts the STFT through the roof! What a fueling strategy Toyota!!! But Clearly the PCM isn't seeing any activity from the O2 at this point.





You would think there would be sensor signal codes being set. Thanks to all who are helping out!

Yeah, that's what I kind of noticed, too. The bank 2 sensor seemed to sit at just slightly lean and then the fuel trims would skyrocket. I think it has to do with the amount of time it's sitting there. A/F ratio sensors can be tricky to diagnose, at least in my experience.

I really think these off brand replacement sensors, $35 vs $115 for a Denso which is actually the cheapest brand RockAuto even sells, is likely the cause of all of this. I kind of resigned myself from this thread when learning that's what was in this but it's an interesting case study, nonetheless, so I found it hard to not keep checking back.

Get rid of these chinese A/F ratio sensors, replace with Denso, and I'm betting the issues go away. There may still be an issue with the MAF but would be much easier to diagnose, knowing the right sensors are in the car to begin with.

I went to the pull apart. Got o2 sensors From 3.0 v6. Spliced it in and ST did not register but Lt was high like usual. Replaced some vac lines that seemed dried out.


The latest oddity is that bank two. LTFT. Increases with acceleration it goes to 50. Some times.

Try swapping injectors from bank 1 to bank 2 see what happens. If it’s going lean under load on bank 2 I’d go after injectors next

Yes. Time to switch o2 bank 1 with bank 2. Only way to settle if the O2 sensor is funky . I’m trying go on vacation Tuesday and wanted to take the van. I have one more day to fix it. Not sure I posted this latest chart. This shows everything kind of ok for 10 minutes , Then bank 2 goes to hades. Bank 2 o2 is filthy black

Swapped o2 sensors out. I was hoping to see someThing new. No change. Bank 2 LT is at 30 at idle and 52 at 2000rpm. Cel code P0174. Sigh....

Random stuff. I read to reset Ecu . Unplugged battery for an hour. Restarted no long term fuel trims for 5 minutes. Then driving around. I get 50 ltft bank one. So the switch moved the high LTFT to bank one Drove some more and the trims became balanced. 33 at 2500. 25 at 900

Well, that pretty much condemns your O2 sensor(s). You can argue it's just one but I'm still betting they are both junk and one is just junkier than the other. You can fix the car but you will need to go get two upstream Denso A/F ratio sensors from your local parts store if you want to drive it on vacation. They will cost significantly more but you don't have time to wait for RockAuto.

Decided to dump in some injector cleaner. Techron. Into tank. Figured a waste of time. Drove about 5 minutes. Engine starts missing. Throws a bunch of codes. Misfire in lots of cyls , Fuel vol reg. P001. By the time I got home engine was purring. Is that crazy! I have never heard of fuel treatment doing anything so fast. Maybe the Techron made fuel pump miss a beat? I still have bad fuel trims. I have a smaller car in case I don’t get Sienna. Audi A4 V6 6 speed manual. Much more fun just smaller I can also just pull plugs on o2 and drive open loop

You will destroy your cats if they're not burned up already.

Decided to dump in some injector cleaner. Techron. Into tank. Figured a waste of time. Drove about 5 minutes. Engine starts missing. Throws a bunch of codes. Misfire in lots of cyls , Fuel vol reg. P001. By the time I got home engine was purring. Is that crazy! I have never heard of fuel treatment doing anything so fast. Maybe the Techron made fuel pump miss a beat? I still have bad fuel trims. I have a smaller car in case I don’t get Sienna. Audi A4 V6 6 speed manual. Much more fun just smaller I can also just pull plugs on o2 and drive open loop

Got a new code Monday! O2 sensor out of range. Go figure...I’ll let van rest a week