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Discussion Starter #1
Hi,
Have a P0174 Code (Bank 2 lean) coming up along with an intermittent C3400 (read with Torque). Shortly after the first time this appeared the Bank 2 A/F heater circuit went open circuit. Bought a new Desno A/F sensor and installed. Codes came back. Cleaned MAF, same. Looked for intake leaks, can't find any. Can PM torque log. Bank 2 STFT seems to stay high for quite awhile after first starting whereas Bank 1 STFT drops pretty quick... Fuel economy is very bad.
Thanks for any feedback / suggestion
 

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Discussion Starter #2
The problem seems to have settled in now. Anytime driving at highway speeds cause Bank 2 Lean condition with Bank 2 LTFT >50%!
Any thoughts / experiences / suggestions?
Anyone have MAF vs throttle position data I could compare to?
 

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I think vacuum leak, either in the manifold, PCV,or EGR. Not sure of the details. I have the 3.3 V6.
 

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Grab some MAF cleaner and clean your MAF up the tube towards the connector and spray for a good 5 count. and test again after letting it dry out for a good half hour - I did mine overnight. I had PO174 with no vacuum leak and only under certain conditions. PO174 at speed can just be a dirty maf and your MAS Air Flow readings look similar to mine at minimal throttle. Also check calculated load if at idle it's high it could be all related. My idle load was 50%
 

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Discussion Starter #6
Thanks for the tip and comparison to your similar problem! I did attempt cleaning the MAF earlier but maybe not good enough?
It is interesting just Bank 2 gets messed up, but maybe that is the algorithm Toyota uses...
I will look at the calculated load values tonight at idle.
I was going to smoke the intake manifold and see if anything obvious shows up. But I will have a look at load and clean the MAF really good first.
 

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Discussion Starter #7 (Edited)
Started vehicle in park and idle, engine load 22%. Removed MAF and cleaned it with newly purchased MAF cleaner. Put a lot on, pools of it coming out... reassembled and idle park similar, maybe 18% to 20% load. have not had the opportunity to hit highway yet.

I have noticed my bank 2 stft goes right up to 20% immediately after the system hits closed loop, while my new AFR sensor for bank 2 sits at 3.3 volts... It takes quite a bit (3+ minutes) of driving (warming up I presume???) for the stft to come down, shortly after which the bank 2 AFR sensor seems to respond and then the stft drops....
Anyone else watch stft when starting? Is this normal? Do I have a faulty (laggish) new AFR sensor?
Bank 1 sensor seems to respond sooner and does not have the stft sit at 20% nearly as long
 

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AvConsult
'02 Highlander V6
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Looking at your data, particularly lines 191, 192, 193, sensor 5 Equiv (lambda) and voltage (i.e. Bank 2 sensor 1) reports a 1.08 LEAN condition at line 191, which predictability slams the trims to +50, for lines 192 and 193.



The trims and lamba improve with high MAF (like line 186), which might indicate a bank 2 vacuum leak.



Is there a Bank2 Sensor 2 PID? That would help determine whether the upstream A/F has calibration issues and falsely reporting lean, or whether a vacuum leak is spiking the lambda.


You also disconnect the Bank2 sensor 1 (A/F sensor), which will force teh PCM to use the bank 1 sensor for both banks. Does that improve Bank 2 fuel trims? Does drivability improve, deteriorate, remain the same?



Fuel trims and MAF at idle in park?
 

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Discussion Starter #9
Thanks for the reply. I will post some more data tomorrow after I format it. Had an interesting two drives today one in the morning and one in the afternoon. I don’t believe there is a bank 2 sensor 2, just the AF sensors on each bank and the O2 sensor further back... i will get some data with it in park and idling as well.
 

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Discussion Starter #10
More data after a drive this morning (some data on the chart is divided by 100 to fit).

MAF and fuel trims in idle at park are at the end of the chart, trims may be messed up since I just finished driving. Hard to see in this mess so: MAF 3.2, B1 STFT -2.34, B1 LTFT -13.28, B2 STFT +1.56, B2 LTFT -2.34, engine load about 20%

I did try disconnecting the front B2 AF sensor and if I recall correctly both bank STFT went to 20% and driveability was poor running this rich (I believe a misfire came up as well when running this rich)... I can try this again to confirm...?

On the chart up until the first arrow, O2 sensor 5 EQ ratio seems quite unresponsive and the B2 STFT goes to +20% for almost this whole time until the B2 LTFT takes over and gets into the 50% range and stft drops, but then at the arrow the O2 sensor 5 EQ seems more responsive and both LTFT and STFT come down. all seems decent after the arrow until the second arrow where I accelerated hard and the B2 STFT goes up to +20% again but not surprising since O2 sensor 5 EQ goes lean at 1.26! whereas bank 1 is rich around 0.9.
 

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Discussion Starter #11
Found an exhaust leak yesterday before the rear o2 sensor. Fixed this.
Data in park: engine load 14%, b1stft: -3.13, b1ltft -6.25, b2stft -3.13, b2ltft +2.34, MAF 3.18, B1 lambda 0.98, B2 lambda 0.96.


Went for a drive, without heavily loading, just slow acceleration. Data attached. STFT B2 climbs to +20% occasionally (first occurrence line 328).
 

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Discussion Starter #12
Smoked the intake manifold and found a leak at the throttle shaft, but only when I turned it by hand. Probably makes sense since my problems seem to come when accelerating hard or driving at high speed.






Is this seal replaceable? Anyone know part number?
Thanks!
 

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AvConsult
'02 Highlander V6
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I wouldn't guess a shaft leak would cause just Bank 2 trims to go wild. A dodgy/sticking injector or a leaking exhaust valve can also cause excess 02 in the bank, and rich trims.


Doubt there is a part number for the shaft seal, at least from Toyota.


Also, your last batches of data are sampled too far apart (6 sec) to get a good feel for events commanding extreme + trims. Need data 0.5 or 0.25 sec apart. Also, helpful to have long and short term trims to determine total trim at any moment.


Because the data is spaced far apart, can't tell why at 06:06 and continuing for 96 seconds, that the after cat 02 sensor is pegged rich, yet the A/F sensors are hovering near neutral lamba (1.00).
 

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Discussion Starter #14
Yes, just bank 2 lean is puzzling but this is the only leak I can find and seems to align with throttle position and when problems start. I can drive fine without issues as long as throttle position doesn't get too high.
There is a picture of an intake runner cut (bandsaw) on clublexus forum (search acis cleaning), the chambers are quite separated.
With various torque logs I have confirmed it is throttle position related. With nothing else to go on, I will try to find a new throttle valve assembly and see what happens....
Intermittent problems are not fun.

Will post my findings...
Again thanks for looking
 

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Discussion Starter #15
Changed the throttle body out. no improvement. trims go high + when driving at 90 + km/h.
Going to swap injectors between banks and see if problem moves.
Could the A/F sensor be faulty at high speeds? I had to replace the Bank 2 AF sensor as the heater circuit in it failed.
I wanted to swap A/F sensors between banks but the Bank 1 sensor is really seized.
 

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Did you ever get this resolved? Are you able to force changes to the STFT? You should get immediate lean changes by pulling a vacuum line and rich changes by adding unburned propane to the intake. That can help determine if the new sensor is doing its job. I'd also double check the part to make they gave you the right sensor.

What are you using to smoke the system?

I'd move away from things that impact both banks, like MAF and throttle body.



Sent from my Moto E (4) Plus using Tapatalk
 
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