I got a check engine light for Bank 1, Sensor 1 cicuit and slow response, and the same with Bank 2, Sensor 1. Considering I can get them online for a fraction of what Lexus is asking, I'm going to do this myself. Does anyone know which is which, in terms of position in the engine compartment/exhaust? I have the option of ordering before or after the cat. Do I need one before and one after, based on the error codes?

edit-
This would probably help - 99 GS400

 

Here's my take:

The after-cat O2 do nothing except check to see the cats still work. Unfortunatly for us, the cat is much more reliable than the O2 sensor. As you have found, it's more likely the O2 sensor will fail than the cat go bad. The front O2s are key compenents to your car's performace, they need to be replaced regularly.

I'd replace the front O2s as part of good maintanince. I'd buy two new O2s and put them on the front of each cat and take the two good O2s that are on your car and move them to the after-cat position.

 

thanks for info VB

is this DIY or no?

 

NICOLA,
The LEFT bank is the DRIVERS' Side on our GS4's, and is called BANK 1, and BANK 2 is the PASSENGER side.

It CAN be done as a DIY, IF you have the O2 Sensor tool, which is essentially a deep well socket with with a cut in the side of it. The cut allows the wires of the sensor to go through it while you are screwing it off and on. There are a couple of styles, but that is the most common.

The left and right sensors should interchange, but the AFTER cat sensor is usually different. I just changed the sensors on a 97 Chevrolet Cavalier Z24 last weekend, and the after cat sensor was really different.


Just my .02 cents

 

One of my secondary sensors just went bad on mine. Changing it is super easy. Just need a 22mm open ended wrench. Definately replace those primary ones as they affect gas mileage. Very odd for both to go bad at the same time though.

 

I was thinking the same thing.

I reset the code(s) and drove a few miles. Light came on again except this time it was for P0171, Bank 1, Lean Condition, along with a very erratic idle. I'm guessing my O2 sensors are fine as they were replaced within the last 10k according to the service records. I'm thinking the MAF has crapped out. I cleaned it already and reset the code, but it came back, as did the idle problem. I also cleaned the TB and the air filter looks fine so its probably the MAF. Wierd that it would give me the code for both O2 sensors

I've been searching the site for referances to idle issues and the idle being low seems pretty common. This is a little different though (and mostly affects the RX people); the idle bounces and the car feels like its misfiring, but the second I give it a hint of gas, it smoothes to a perfect idle. Its hovering around 650 as a guess (a little above 3rd line?) so I don't think its low. Maybe its the TPS? I get around 14.8 at idle and 80.8 at WOT. Is this within spec?

Anyway, the MAF was ordered tonight so I'll see how it goes tomorrow.

Sorry for all the questions btw, I think I just need to get the FSM

 

This has been driving me nuts. Today - Replaced O2 sensors, MAF, cleaned TB (and ran SeaFoam through intake - this stuff smoked out my whole neighborhood!), plugs are fine, checked for vacuum leaks and I'm still getting code P0171 - System Too Lean .

I'm going to try to spray carb choke tomorrow all over the vacuum lines to see if I missed a leak, but I doubt its the problem; I'm not hearing anything. Ran my OBD scanner again and fuel trim at idle is around 18%. Shouldn't this be around 10%? Anyone have numbers I can compare? The only thing I can think of is a exhaust leak somewhere near the front of the pipes, but the car is silent in that regard. Other then that, I'm out of ideas... Any suggestions?

 

I ordered the electrical manual for ny GS430. I've worked on two OBDII cars now (the GS is my third) and I've found that without the manual it's difficult to overcome these kind of issues. The manual has a specific set of steps to find the problem. Lean conditons can be caused by a bad injector diver, a bad O2 or a few other things.

 

I know you stated that you have checked vacuum leaks, but look again closely. You can have a vacuum leak BEFORE the throttle body and/or AFTER it, which will affect the system and give a P0171 code.

Check the hose from the intake to the brake booster, the seal around the air cleaner before the mass air sensor, and definitely AFTER the mass air sensor. I found mine loose one time, and that gave me problems. Be sure to check the four bolts holding the throttle body to the intake manifold. In fact, I would change the gasket there, because that has leaked before at that point, and introduced EXTRA air into the system.

The 02 sensor sees that extra oxygen and has to register it as a fault and sets the code. I even used soap bubbles on my 2000 VW Beetle to find the leak. I used a small spray bottle with a little water and some dish soap mixed up. I sprayed it on an idling engine, and it amplified the hiss of the vacuum leak.

I am not saying that a vacuum leak from a hose is your problem, but it is definitely possible. Try to rule out any vacuum leaks first, and then troubleshoot further.

HAPPY HUNTING!!.

 

Thanks for the suggestions. I believe I 'found' the problem, but I'll have to try your soap method for sure. It seems to be coming from the driver side of the engine, where the injectors and intake manifold are. There is a small box with '12v Toyota' written on it, one electrical connector and two vacuum hoses. Its either this box or the intake manifold gasket, I can't control the spray from the carb choke enough to pinpoint it. I will def. try the soap though. Has anyone heard of this happening before? A bad gasket on the manifold will explain the code and rough idle...

 

I have not personally heard of our engine leaking in that area, but it IS possible, though not likely.

I used to use carb cleaner to find vacuum leaks until one day some of the spray contacted a hot exhaust manifold, and I had a mini-fire to put out. I use soap and water now.

Put it around the area in question...BE SURE some of the water gets around it, as well as the bubbles, and if leaking, you can hear the intake vacuum sucking the water in loudly.

This has really worked for me. Go around all the vacuum components with this concoction, and if there IS a leak, you'll find it. Don't worry, a LITTLE water won't hurt anything.


GOOD :LUCK AGAIN

 

Check for any leaks between the MAF and the TB. If you have a loose connection or leak, you'll run super lean and throw a system too lean code as well as variety of other codes.

 

The problem has been solved - turns out it was 2 bad injector o-rings.

I tried the following today with my mechanic -
-replace intake gasket (flange and top section) - no dice
-triple check vacuum lines for cracks
-O2 sensor wiring (new sensors were dropped in last week)
-MAF (last week)
-new plugs

None of these solved it.

I had be spraying carb cleaner all over the intake manifold and it was dying, but this continued even after the new gaskets, so I was really hard up for an explaination. I took a piece of hose and listened to pieces of the manifold, and noticed it got louder when I was nearer to injectors 1 and 2 on the bank 1 side (driver). I sprayed the carb cleaner right onto injector 1 and it stuttered., same with two... the rest were fine. I guess the stuff was pooling at the o-rings when I thought I was hitting the gaskets...

We took off the fuel rail and the rings were pretty beat up. Since new injectors are the only way to get this O-ring (or so we were told by my Lexus dealer), we just put some silicone on each ring as a sealer until I can ghetto rig something permanent. Unless, of course, one of you knows where the hell I can get the O-ring kit for the injectors

Idle is perfectly smooth, as is starting up. Just a heads up to those of you with idle issues - maybe the o-rings on your car aren't bad enough to lean out the car to the point of a check engine light, but are causing enough of an issue to introduce a low idle...

Thanks again for those who replied.

 

hey what up this is dee i just checked my injectors as well i have 5 bad ones i just called my friend at lexus and he said they do have just the O ring kit i am going to go pick them up right now let me know if you need a kit i can get you one.

 

great info

thanks alot im going to check out my injectors real soon

have you fixed yours yet ?