I created the same thread in the GS300 section but noone seems to kno the answers, hoping someone here can help. below was the previous thread started about the issue.

https://www.clublexus.com/forums/sho...d.php?t=394077

 

nope... not the air flow meter....

I would check voltage response from the o2 sensors first... typically it's one of the upstream sensors...

 

I responded to your original thread that was only created... a few hours before this one... I know you love your car but have some patience man. Reset the light by disconnecting the battery... if it comes back on you'll probably need to change your coolant temp sensor...

 

That is initially what I thought as well, though in the real world, it seems as though this code is very misleading, and out of all the posted fixes in identifix, it has always been an O2 sensor causing the issue, thus my recommendation to start there... if voltage is good, then it could either be a coolant temp sensor, or, as the weather has been getting cooler, it could also be a thermostat stuck partially or fully open...

 

Thanks for the recommendations, I was a little anxious since only 1 store was still open last night and I use this vehicle as a daily driver I spologize for the multiple threads. I did not want to get stranded somewhere if the car fails or what not. But as Djspawn said, since those are not A/F sensors I would not have to worry it has anything to do with a O2? Im going to replace the ect sensor "coolant temp sensor" first. i that does nothing then ill bring the vehicle in for service since my o2's are pretty much seized in there and require a impact wrench to remove.

 

man, I hate to say it like this, but YOU asked for our help...

that you ignore it, well, it's gonna cost ya money...

you are throwing parts at a problem that you do not know the full workings of... when we have a problem like this, spending 30 minutes testing a few things will greatly reduce the money you spend on attempts... all you need is a $10 radio shack voltmeter to test the o2 sensors, if you'd like help doing the diag, post back here, but if you don't at least check the voltage on the o2 sensors first, you might as well have not asked for help here...

 

also, an impact on an o2 sensor is asking for a stripped manifold... get the car hot, and as it cools, spray some PB Blaster on the o2 sensor threads... while it is still hot/warm, remove the o2 sensor... there are special sockets (not impact rated) made for this, or, many times, a large wrench works better...

 

ive actually treid removing the O2 today, loan a tool 24' breaker bar from atuozone w/ the o2 socket removal no good, its dead stuck on there to the point it feels like im stripping the bolt so i stopped. Im not familiar with electrical & how to read the voltmeters thats why i tried avoiding that route, im not trying to ignore the help just not familiar with the electrical parts. i can try again on Monday to borrow a voltmeter and give it a go.

Another thing is theres 2 different paths on resolving the P0125, some individuals are saying its the ECT & others are saying its the O2 as how you and Djspawn agreed upon the 2 solutions as well. and the ect is a much cheaper part to replace @ 35$'s from pepboys towards the 97$ O2 from sparkplugs.com

where exactly is the ECT sensor located?? and by following this site http://bahamutcars.free.fr/workshop/...nts/index.html it states to connect the o2 to the voltmeter, rev to 4k rpm 3 times, and see if it goes over .45v atleast once? if yes it leads down a tree stating to replace the bank1 sensor 2 O2? is this the correct method to use? I work a weekend shift and would not be able to get to a autozone till Monday. Thanks again for the help.

 

I've actually heard of the GS's having issues with frozen o2 sensors in the manifolds... PB Blaster is your friend... use a lot of it... multiple times...

Easy way to test o2 sensors - should be a 4 wire sensor - one should fluctuate between .1 and .9 volts, and two others should have resistance between them, which will depend on the temperature they are tested at - typically 10 ohms or more between the two... test for resistance without the sensor plugged in, test for voltage with the car running... their test is for after cat sensors... Sensor 2 is a downstream sensor and shouldn't cause your problem - most likely it's a Sensor 1 (bank 1 or 2)... Bank 1 is one side of the engine, bank 2 is the other side, sensor 1 is before the catalytic convert, sensor 2 is after the catalytic converter...

anyways, watched on a voltmeter, you should see a sweep that ranges from less than .5 volts to more than .5 volts... typically it'll be like .2 volts then .8 volts, then .2 volts, then .8 volts... it'll cycle back and forth once or twice a second...

 

Just yesterday night a cel came on, i quickly managed to get to autozone before they closed and recorded a "P0125 Insufficient coolant temperature for close loop fuel control" code
The code is for coolant temp. In order for the car to go into closed loop operation, it must be at operating temp. There are two things that can cause this problem. The first is the termostat stuck open, the second is the temp sensor itself. Keep in mind that the engine computer uses a separate temp sensor, from the one on the instrument pannel.
The first thing to look at, "is the temp gauge running at it's normal position"? Or is it lower than normal? If it is lower than normal, it is normally the thermostat stuck open. Get a replacement, make sure it is for 195 deg, pay carefull attention when taking the old one out. On a typical car, the thermostat can be installed upside down, of course this causes overheating.
If the gauge is running at it's normal position, then check out the engine computer temp sensor.
I am sorry to say, but these codes do not have anything to do with the O2 sensors, although I can understand some confusion on this. Since OBDii cars came out, they have used 4 wire O2 sensors (except for the newest style wide band sensors). The 4 wire sensors have a heater built into the sensor. The idea of the heater is to bring the O2 sensor up to operating temp sooner so that the car can go into closed loop operation sooner. The computer monitors the heater current and will generate a similar code if it determines that the current is not correct.

 

Oh really, they don't have anything to do with it?

How come out of three instances on Identifix, all three times were fixed with an o2 sensor replacement? I don't know all the reasons, but it seems even on OBD Codes, it's even mentioned there as an o2 sensor issue... here's Identifix's history:

Vehicle Description: 2000 Lexus GS300 3.0L

Mileage: 151000

Customer Concern:
Check Engine Light is on. Code P0125. Bank 1 Sensor 1 (B1S1) O2 sensor reads 0 volts on the scanner and with a voltmeter. Sensor voltage does not respond to supplemental fuel.


Tests/Procedures:
1. Unplug the B1S1 O2 Sensor and check bias voltage to it from the Computer on the Black signal wire. Can compare to B2S1 O2 sensor bias voltage from the computer on the White signal wire.

2. Can check the B1S1 O2 Sensor Black signal wire for continuity to ground. Verify that it is NOT grounded.

3. Can unplug the B1S1 O2 Sensor and check for voltage right out of the sensor - it is a zirconium style O2 sensor, so it should generate its own voltage.


Potential Causes:
B1S1 O2 sensor
Wiring harness


Diagnostic Codes:
P0125


User Comments:

Close Comment(s)


Category:

Engine Performance
Diagnostic Codes



Call Taken By: Paul Kujawa

Call Date: 6/8/2006

Key Number: 165630


User Comments



Posted By:
What Fixed It / Confirmed Fix




Sheron Dunn
3/26/2008
1999 Lexus GS300 3.0L *
Front Oxygen Sensor
Replaced front oxygen sensors only.




Rhett Valentine
9/13/2007
2001 Lexus GS300 3.0L *
Oxygen sensor
replaced all o2 sensors




Michael Duwel
8/29/2007
2000 Lexus GS300 3.0L *
O2 Sensor(s)
OXYGEN SENSOR REPAIRS *DUWEL AUTOMOTIVE

 

I am not familair with Identifix, I have mainly used Alldata over the years. I looked up P0125 for a 03 gs300 and it states that the error code is for coolant temp. Unfortunenatly I do not have access to Mitchell On Demand at this time, because one of our sources is obviously wrong. I have worked with Alldata enough years to realize that more than once it was wrong, you could very well be correct. But at the start of this thread, it was mentioned that Autozone told they that this code is for coolant temp. I wonder where Autozone gets their codes from?

 

This is the first time that I have tried to attach a file, but if this works, this is what alldata has on this code

 

You have to remember one thing - most of those tests are for generic obd2 codes... This is why you can't just replace the part that the code says is the problem on obd2 systems anymore (with obd1, if the light was on for a problem, typically, you could replace that part and be good to go), but with obd2 systems, they are very misleading and some of the codes require different values to be achieved between different vehicles (even within the same manufacturer).

I would bet, given the information from Identifix (which is a collaboration of repair shops nationwide - a database of problems they ran into and what it took to fix them, as well as alldata/mitchell type information), that there is something in the ECU's programming that says to set that code if an o2 sensor comes out of range as well, but maybe within a certain value that says the o2 sensor is still operating, thus not to throw a code for the sensor itself...

This is why I always test the related components, get information on potential related failures from Identifix, before I give a customer a report on what is truly wrong with their car. I learned my lesson a long time ago - fully, properly diagnose a vehicle else you will have an unhappy customer. It is because of this that I steal much business from other shops that shoot for the easy fix...

Keep in mind, I'm not saying it's not the coolant temp sensor, as it very well may be - only testing will tell for sure; but there are other potential causes that should be investigated first... How would you like to throw parts at it and none of them be the issue... I've had customers come in with a book full of receipts from autozone of parts they replaced that autozone told them to based on problem codes, and all it was was a $10 PCV hose elbow (Fords are notorious for setting a system lean and misfire code because they are sucking in unmetered air through this elbow, which sits in a hard to see spot). Last customer I had with one of those engines (it was an expedition) had replaced spark plugs, all 8 coils, all 4 o2 sensors, and the mass air flow sensor... Ten minutes into the diagnostic, I noticed that elbow was leaking, advised the customer, replaced the elbow, everything is fine. He spent probably $1000 on parts that were probably never bad, when a $10 dealer part was all it took... I've also had customers do the same and replace almost every sensor on the car, when the ECU was at fault... ECU's aren't expensive and I hate relaying that to a customer, but it costs a lot more after you've already replaced a bunch of parts that didn't need to be replaced to start with...

long story short - test everything related, determine the failure, then replace what actually failed...

 

True I agree. Unfortunaltly we do not have acess to the car, it would take only a few min to determine if the temp sensor was displaying the correct temp. Much more difficult to troubleshoot by remote.