On 2004 lexus ES330. I have engine code P0171 which could be a lot of things but everyone seems to say it is an O2 sensor. I do not know where that specific sensor is located and what the part number is, if it turns out to be the cause. Nevertheless, I like to add what happened which could possibly be the cause for this code. Last week, when all was well with the car, no engine code, other than time to have an oil change, my son changed the oil. Then with the gas blower he was cleaning the garage but forgetting the oil pan full of used oil is sitting beneath the car. By the time we discovered it, almost one or two quarts of the oil was splashed all over the exhaust and front passenger inner tire and all over the bottom of the car and floor. We cleaned all we could using simple green and shoprage, but the car has been burning that residual oil left on places creating horrible smells after driving and getting the exhaust hot. However, a week after that, the code appeared and more cleaning did not help. I wonder if that oil splash was a related cause or the O2 going bad happened to be coincidental. Need any advice possible and location and the part number please, if you don't think changing the sensor is not a waste of time. Thanks.

 

What year? Before you declare the O2 sensors dead make sure the connectors are clean and don't have any oil in them.

 

Sorry, 2004 ES330. Good point about connectors, but wouldn't the water from roads cause the same problem? BTW, I have no idea of the location for the sensor or its connector.

 

I checked the connectors for all four sensors. I found a diagram showing all; bank 2 &1 heated O2 sensors 2, their connectors were near one another, then the third one bank 2 sensor 1, fuel ratio sensor near the battery. The last one bank1 sensor 1 near the fire wall, about the center, after the catalytic converter. The heated ones, I could only see 13.4 ohms on the black lead with the engine cool and off. The other two, fuel ration ones, the black leads read 2.7 ohms, All four connectors were clean, no oil had entered them. Any input appreciated. Does the code P0171 point to the O2 on bank1 or Fuel to air ratio sensor? Is it logical to replace the Bank 1, O2 sensor even though it reads the same ohmic value as the bank 2 does? The output voltage is unknown at this point.

 

Hello,

There could be a number of causes for a Lean Code, and not all of them are related to the A/F sensor, your car should more or less be advanced enough to be able to determine if the sensor's Performance is not on par, at least if it is enough to trigger Lean Code.

By checking the Resistance of the sensor, you only check the resistance of the Heater Element inside of it, essentially a coil that would pre-heat it before the engine warms up, with that, the sensor could remain functional even without the heater element. The only way I know if to check them is to look at the Engine Live Data and make sure that the parameters the sensor gives out are in check.

Start by using OBD2 Scan Tool and watching the Engine Live Data, Fuel Trims and A/F sensor readouts specifically. See what Long Term Fuel Trims you have, and that both Bank 1 and Bank 2 sensors respond quickly and in a similar manner when you abruptly press and release the Gas pedal, if there is a delay in one of the sensors, or the readings are considerably different, that could be a sign to replace the A/F sensor.

What you can also do is try disconnecting the Bank 1 Sensor completely, and see if the car's behavior would change, while it won't run perfectly, if you feel a noticeable difference and see the Fuel Trims get closer to the norm, that could also be an indication of a bad sensor.

As for how spilled oil ties into this, it's probably a coincidence, A/F sensors do have a finite lifespan, even if the ECU is not throwing any codes, it doesn't mean that they are performing perfectly, sometimes the readings can start drifting in one way or the other over time, but still be within the ECU's tolerance, even if the engine doesn't run perfectly, my 2000 ES300 greatly benefited from two new A/F sensors, even though there was no code, only the Fuel Trims being a little off.

There is also a reason why not all GM vehicles have turned into dust at this point, all thanks to the built-in anti-rust technology integrated into all the seals on the engine and transmission, allowing part of the oil that would otherwise burn in the engine to be evenly distributed all over the undercarriage.

Hope this helps and best of luck!

 

You will need a high end scan tool or Techstream software. A Japan car specialty shop will have it. This isn't a diagnosis for an average shade tree mechanic.

 

Which brand A/F did you purchase?

 

I got the ones linked below for both banks.

https://www.rockauto.com/en/moreinfo...1&cc=0&pt=5132

Hope this helps and best of luck!

 

Thanks Arsenii for your feedback. I need to get a scanner for all those details. The part store helped me copy down the "Freeze data" and "Live data" information from their scanner. This code being the P0171, showing the O2 for bank 1 sensor 2 to be good but O2 for bank2 sensor 2 shows zero. I pulled the MAF sensor out and the thermoister looked dirty and the other two resistors way down below were just a little. Cleaned them and rested the EMC with battery disconnect to see if that cleaning helped.

FREEZE FRAME (engine off)
FUELSYS1 CL

FUELSYS2 CL

LOAD_PCT 9.40%

ECT 85 C

SHRTFT1 10.90%

LONGFT1 32.00%

SHRTFT2 12.50%

LONGFT2 35.10%

RPM 708RMP

VSS Okm/h

SPARKADV 17.5 deg

IAT 32 C

MAF 2.25 g/s

TP 14.5%

I/M REAINESS

MIL STS on

MISFIRE OK

FUELSYS OK

COUP CMPT OK

CATALYST INC

HEATED CATALYST N/A

EVAP STS INC

2ND AIR SYS N/A

A/C SYS REF N/A

O2 SNSR INC

O2 SNSR HEATER OK

EGR SYS N/A

Live Data

DTC 2

MIL SYS MIL ON

FUEL SYS1 CL

FUEL SYS2 CL

LOAD_PCT 12.20%

ECT 60 C

SHRTFT1 0.80%

LONGFT1 34.40%

SHRTFT2 3.10%

LONGFT2 38.30%

RMP 718 RPM

VSS 0 km/h

SPARKADV 15.0 deg

IAT 21 C

MAF 2.62 g/s

TP 14.30%

O2SLOC

O2B1S2 0.74 V

SHRTFTB1S2 99.20%

O2B2S2 0.0 V

OBDSUP

EQ RATB1S1 1.001

O2B1S1 3.2 V

EQ RATB2S1 1

O2B2S1 3.24 V

 

Sorry for the delay.

From the data listed above, both of your Fuel Trims are pretty high, both banks experience a similar condition, it's just that one of them is a tad bit higher, enough to trigger the Lean code on Bank 1.

Your MAF sensor readouts at Idle are way too low, they should be closer to at least 3.3 - 4 g/s at Idle in Park. That is usually a sign of a Vacuum Leak somewhere in the engine, look for a loose hose or any hissing sound from the engine, anything that could result in a relatively substantial leak. Other way to test it would be to start up the car and plug the intake, it should stall almost immediately, if it takes a while, or it doesn't stall at all, you do have a vacuum leak somewhere.

Hope this helps and best of luck!

 

Hi Arsenii, Thanks for your input. About the "plug the intake", would that be right after the MAF sensor (excluding it) or anywhere after the air filter? BTW, I talked to my son who did the oil change who is back to his state far off, he apparently blew air into the engine to push the residual oil out with the gas blower, would that cause anything in relation to this code? He did not think so but he wanted me to ask.
Thanks.

 

Emmmm, yeeees, yes it will.. I've never heard of anything like that frankly, the Oil System is not designed for such a flow, and a blown PCV (Positive Crankcase Ventilation) hose will create a gaping hole in the intake, which will for sure cause a Vacuum Leak.

Check the two hoses that connect to said system, one is on the Front of the engine, connecting straight to the Front Valve Cover, the other one is on the Back of the engine, on the Passenger side, there is a small piece that goes from the Intake to the PCV Valve, which is threaded into the Back Valve Cover, I would assume that it is the latter that got blown off, as it is located after the Throttle Body, and would give a more noticeable effect, as there is no vacuum before it.

And just for the future, please don't do that again, you will be lucky enough if it is just the hose that blew off, but there could be other damage if you continue to blow air into the engine the way it was done. If you really want to take All the oil out of the engine (which there is no real need for by the way), just use a big syringe with a hose on the end, going through the Drain Plug.

I would try to keep the MAF in place, as long as you take care not to damage it in the process, but it could be done with the MAF off, the engine won't run quite right though, which may interfere a little bit.

Hope this helps and best of luck!

 

Thanks for keeping up Arsenii. Good advice, but it only happens during long holidays when I may get help from my son during his visit. He is in the Army and they apparently do that to military vehicles in a rush job, however, I do not know. He claims the oil drain plugs were open to avoid pressure build up and it should have not blown out that hose. Based on your advice, I tried to find something called PCV. Isn't that a one-way-vacuum-valve? The closest thing I came up with was on the passenger side by the firewall beneath the "Fuel Injection Plenum" space on the engine back cover (very tight place) which I am attaching a picture for your verification. The other one in the front, "one is on the Front of the engine, connecting straight to the Front Valve Cover", can you please attach a picture or a diagram for me to locate it? The PCV looks attached to the valve, but I am not sure if the other end of the hose. Can it come loose, will it, if the valve is one way? The second picture was taken with the open to capture the other side of the hose from the PCV valve.

Thanks

 

take several pictures of the whole engine bay - with this cover removed

 

Huh, I've never heard of it before frankly.. In any case, ES is not really a military truck, and the path the oil travels to the drain plug is not always as straightforward, especially if it is the diesel truck, hence the suggestion from earlier.

It is, but it is placed in reverse, allowing the Oil Fumes to travel From the Engine to the Intake Plenum when there is vacuum in it, with the purpose of it in there being to not allow excess pressure to go from the Intake into the Engine when it is at higher RPM, or when the throttle is wide open, so if you blow into the Oil System, the pressure would still find its way into the Intake.

Yes, it is the PCV valve and its hose, they appear to be attached. I would still check it though, as I've had cases of them drying out and cracking, causing a leak as well. Just pull on that hose, make sure it is intact and secure.



Here is a Diagram that shows both PCV hoses. And as fortitude mentioned earlier, it would be helpful to take a couple of pictures around the engine bay, mostly of the hoses around it, to see if there is anything loose.

Other than that, here is a diagram of the majority of Vacuum Hoses around your engine. There should also be a sticker somewhere on the hood showing a block diagram of where it all connects to.

Hope this helps and best of luck!