kford1040

I know no question is supposed to be a dumb one but I don't understand can anyone explain the Technical Service Bulletins? I came across something in my OCD-like research that refers to A/F and O2 sensors and Threshold Values and sensor ID but I don't know what that means. There was also an ECU Programming procedure that may not be relevant.

2000 Lexus Truck RX 300 AWD V6-3.0L (1MZ-FE) Recall and Technical Service Bulletin Titles

TSB Number & Issue Date TSB Title
I know there is a post elsewhere regarding the bulletins but here is a link with recent TSB, which even has something referencing key casing.

http://www.alldatadiy.com/TSB/74/00740506.html

Again, sorry if I'm asking a question that's already been answered. But I know I'm not the only one going in circles regarding these sensors and I just want to make sure there isn't something I'm missing regarding these Bulletins. Clearly something is going on with my car and it's 0171 error but this guesswork is like playing darts blindfolded in a crowded room.

hypervish

The TSB's won't help much now, because they can only be performed under warranty.

As per the P0171 have you tried cleaning the MAF sensor?

artbuc

P0171 can be difficult to resolve but your question about A/F sensors was already answered on the first thread you started. You also got some very good advice on that thread. You will not find a TSB or any other document which will tell you exactly why your car is throwing P0171. There are many potential causes. First rule out the MAF and then have your fuel supply system checked by someone who has the proper tools and knowledge. Forget about your A/F sensors and O2 sensors until/unless you get a specific code. If you want to increase your knowledge about A/F sensors (you have two) and O2 sensors (you have one) you can search this forum and you will find pictures, DIY replacement help, DTC codes, etc. It is a remote possibility that you have a "lazy" A/F sensor which is causing P0171 but not "lazy" enough to throw its own trouble code. A bad A/F sensor will affect engine performance. A bad O2 sensor will not affect engine performance. The fact that your car idles fine but performs poorly under load/acceleration and your ECU is trying to compensate by maxing out fuel trims is your best clue.

kford1040

So in theory if there is something that was done to correct the A/F sensor readings - it looks like the same Bank 1 sensor was replaced by the dealer in 06. And if you didn't have an extended warranty how would the '09 Bulletin apply? Not trying to be a PITA just curious.
Also if there had been something that they had fixed in ECU but then I had battery issues (twice) would that totally wipe out any updates?

As for the MAF sensor i couldn't get it unplugged. so I cleaned it as best i could but now based on further reading I'm guessing it's not really cleaned.

I've had multiple sensor errors come up since last spring but the 0171 (a lean fuel bank) is always there. So my belief is that it's still the calculation causing the bad readings or slow circuit not actually bad sensors.

(i'm not a mechanic - I just pretend to know what I'm talking about)...

Kimberly

artbuc

Do you have multiple error codes now? Do you know how to clean a MAF?

kford1040

I took the MAF Sensor off again and it was fairly clean compared to the first time but I was still unable to actually unplug the sensor. I used CRC MAF Sensor Cleaner and put towels under it since I couldn't get it off. I let it dry. I stuck nothing down it either time.

I put it back on and made sure it was positioned well and tight. Also I noticed that the hose clamp behind it was loose so i tightened that as well.

I cleared the codes and was hopeful as I left for errands. Still tripped the CEL as soon as I braked once.

I will see about the PCV and figure out how to actually get the MAF sensor off but in that other thread I was trying to get an idea of what the A/F Sensor Voltage is supposed to be in Bank 1 position 1 and 2 as well as the 02 Voltage since mine the Bank 1/1 is reading 0.4-0.8 and the bank 1/2 is in the 3.3 + range (the O2 is similar).
I don't know if that's normal or 'lazy' like you said and means just replace the bank 1 sensor.
I've tried to find the right readings for them and just found generic info.

Off to Sears for tools that I don't have .

artbuc

For the third time, do you know how to clean your MAF? IOW, do you know specifically what needs to be cleaned? When you last "tripped" a code, what was it (were they)?

Here is some good info re A/F and O2 sensors:

www.autoshop101.com/forms/h37.pdf

Your voltage measurements are confusing. Bank1Sensor1 and Bank2Sensor1 are A/F sensors; Bank1Sensor2 is an O2 sensor. Are you getting about 3.3 volts on both A/F sensors?

kford1040

I thought I had answered that I understood how to clean the MAF other than I could not get it off after I took the screws out. The red diodes looked fine and i stuck nothing up there when I sprayed the cleaner. If I missed something in the instructions that I read then I'm all ears.
I still ONLY get an 0171 error sometimes twice. Sometimes I don't bother clearing the CEL since it doesn't matter.
I trip 0171 every time I drive - it is just a matter of when. It may be the first time I decelerate and or brake or it may be 30 min/miles into my drive before I'm not allowed to go into overdrive. It doesn't matter if I've cleared the code or not - the behavior is the same and I haven't been able to determine the trigger since the Actron I bought only does live data - doesn't actually allow for download.
In the past I have had the knock sensor in bank 1 the same as 0171. But I think that goes off because the fuel is lean and it's a secondary error when I was accelerating uphill. It also doesn't return when I clear the codes.
As for the readings - I typed them just like they were displayed on the Actron I didn't realize it was just an expensive a code reader for what it really does.

I'm pretty sure based on what I've read and what's already been replaced that this is an open circuit issue with the bank 1 A/F sensor and it triggering the lean fuel.

Anyway once it's replace along with the spark plugs I'll let everyone know.

artbuc

Will be interested in your outcome. If your B1S1 was .4-.8 volts something is wrong. However, I suspect that reading was from B1S2 which would be correct. In any event, I have never heard of a bad A/F sensor which didn't throw its own code but that doesn't necessarily mean it has never happened. OTOH, there are many examples of faulty MAF sensors which have symptoms exactly like yours. Good luck and keep fuel supply on your list of potential suspects..

hypervish

It may be time to just go ahead and replace the maf sensor outright. But then again that would be throwing parts at it, and that's not something you should do.
Maf sensors can go bad, and sometimes cleaning it won't help.

kford1040

That's what I was trying to prevent... (since now I have my 92 Prelude that is going to require body and unknown mechanical work all out of pocket...

I found an example of our MAF sensor and other than the fact that I can't get mine UNPLUGGED! ergg... that's pretty much what I did.. though I am aware that the light doesn't just 'go off...

Anyway, we'll see how today goes... it's 21 degrees here and I'm really regretting cutting off the air vents to my garage at the moment (though it was a code violation). So I'm procrastinating a little bit.

kford1040

Since I cleaned the MAF Sensor I'm not tripping the CEL yet but maybe not driving far/fast enough but I'm also not going into overdrive at all

Bank 1 Sensor 2 are anywhere from 0.020-0.9 and the mechanic has replaced twice.

What seems' to happen is that there is a slow response between the two sensors ... I saw on the dealers page that Sensor 1 was replaced in 2006 but seems to me they should have both been done at the same time. Bank 1 Sensor1 stays drops as low as 2.7 to 3.5 and I don't know if somewhere between the two is where the 'slow' circuit response is which is what triggers the lean fuel.

One other thing when I redid the MAF Sensor and tightened the hose clamp last night I noticed that if I revved the engine it no longer had that initial hesitation.

amblyn

Measure the resistance of the af sensors if you google it you will find wht they should be but if it is 0 or open then its bad. but if you have a bad af sensor ud have alot more then just a code.

So for maf sensor squeeze the tab very hard and try pulling off while maf is screwed into box still. also look up iacv cleaning try that. make sure theres no vacume hoses leaking like the hose behing airintake box that comes off alot good luck

artbuc

Are we talking about the same sensors? .2-.8 sounds right for B1S2. B1S2 is the O2 sensor downstream of the cat converter. It does not affect how your engine runs. One thing we have not discussed is the brand of A/F or O2 sensor. It is generally accepted that aftermarket sensors do not work in Toyota vehicles. Eg, many reports of Bosch sensors causing trouble codes. If you do replace, make sure you use factory or Denso which is identical to factory. 3.3+/- is right for B1S1 and B2S1, your A/F sensors which are upstream of your cat converter.

Also, absolutely no need to replace both A/F sensors just because one is bad.

kford1040

Well just want to say I have no idea what these readings are but I'm not getting an error code but my mpg is now at 9.....
My bank 1 a/f 2 fluctuated as low as 0.030-0.8x
Bank 1 a/f 1 dropped 2.7-3.33

I went maybe ten miles.

Just thought I would throw that in the mix.