Check Engine Light Came On Today....

[Phil E]

Thanks RX. I took your advice and contacted both a professional mechanic friend and a Lexus service manager today. Both advised me not to put in any fuel additives as possibly doing more harm than good. (Go figure.) My friend said it was highly unlikely my injectors were dirty and the Lexus guy concurred. Intrestingly, he said that in all his years at Lexus, he had never before seen a "system too rich" trouble code and advised me to bring it in and they'd check for a disconnected vacuum hose. Since they want $90 for that service, I'll first take a look myself over the weekend. I also asked if it could have anything to do with the O-2 sensors and he said he didn't think so. As I mentioned previously, the car seems to be running fine, although possibly going through more gas.

Any other ideas out there?

[lexus_romeo]

I too feel like I'm burning thru more gas. I put 87. 99RXAWD bought new, now w/65k mi

[APN]

I too feel like I'm burning thru more gas. I put 87. 99RXAWD bought new, now w/65k mi

I think cleaning the MAF is easy and quick enough, it doesn't hurt. I removed the 2 scews and took the MAF sensor off the air filter housing, used a Q tip dampened with contact cleaner to clean the visible metal contact and the tiny wire sensor located at the top of the sensor housing (looking up from the bottom of the sensor). Then I gently dried off the cleaned parts using canned compressed air. Ten minutes job. Reset the CEL and it has not returned for few days now; engine knocking is gone. I could see the black deposit removed from the sensor parts on the Q-tip.

BTW, can anyone show me how to replace the spark plugs on the RX300.

Thanks to everyone for your advise with my CEL issue.

[RX99inLA]

Hi there,

I too have an RX 300 with over 100K mileage. I got the P1135 code too, which is the O2 sensor. We also found out that we didn't have enough coolant put into the car. They might be related. Anyways, Autozone estimated $450 for the bank 1 part. :whistles: Well, in the case that I would have to replace the bank 1, can anyone tell me where to buy a cheap one and also how to figure which of the 2(or 3) bank 1's to replace?

Thanks much in advance.

[ndnlex]

New to LOC, however found much in the way of assistant and enjoyment, thanks to all how take part.

Our 2000 RX300 has the same issue with O2 sensors (Air/Fuel Ratio Sensor). Where when they go bad your engine loses much in the way of performance, and fuel efficiency. Lexus diagnosed the problem as system lean bank 1, in addition the codes also read cylinders 2, 4, and 6 misfiring. The on board system computer attempted to correct this. However when the misfiring occurs often enough the system computer can not adequately adjust enough for the problem.

We did replace all 3 O2 sensors, 2 in front of the CAT, and 1 aft the CAT. To my surprise only after 115 miles the check engine light comes on. I then read the codes again, P0171, P0441, P0444, P0446, "Bank 1 Lean" and "Cylinders 1, 3, and 5 misfiring" I understand that some code readers run generic system test, and they vary. At this point I contacted Lexus Customer Service and asked "What is going on here, please help." Maintaining a very polite and respectful manner. They researched the vehicle maintenance history and found that just prior to my purchase, less than a year the O2 sensors were also replaced by the previous owner. Wow, did I blow my top. How is it possible that my local Lexus tech would recommend a solution, when that same solution has been only recently done without actually being the correct solution. Well needless to say, at this point Lexus Customer Service said that they would follow up with the local dealer and seek applying a Goodwill warranty. So here I sit waiting for the call. I will keep you folks updated as this issue unfolds.

[jimmouse]

Just spoke with our Lexus service manager again.  The culprit was indeed the Air/Fuel Ratio Sensor (also called the Bank 1 Sensor).  Those of you with RX300s should note that trouble codes P01130 and P01135 indicate problems with this particular sensor.  It's good to know that AutoZone's code analyzer got it right in our case.

My wife will pick up her vehicle this afternoon.  Hopefully our sensor problems have been resolved for awhile.  I'll document this information in my files, and ask that those of you who are able to crosscheck other trouble codes with the other sensors on the RX300 please post on this forum so we can all build our own trouble code libraries.

Diagnosis is the key  -  once you know what you're dealing with, you can make the decision on how you're going to go about fixing the problem.

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When I was using KN filter, every time after I cleaned MAF, I got 1130 code. If I disconnect the battery to clean the code, it will not show again unless I clean the MAF again. Recently I read some thing about the filter then I decided to use paper filter. Now after I clean the MAF, no code any more.

[jimmouse]

RX in NC,

Thank you for the head up with various sensors problems.  So far I was able to clean the IACV and the MAF.  No more engine check light for now, but I'm sure I will run into your problem soon (my rx300 is at 73K miles).  Please keep us update with what dealer replaced on your rx300.

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oldrx300,

how did you clean the iacv? On my 2001 RX with 76k miles, the two screw has rust on it. I can not unscrew it.

Thanks a lot.

[danigirl]

I am a new RX300 owner purchaesed last July, curently at 61K and check engine light on. P1133, I changed the O2 sensor(behind firewall) w/ Bosch Part 13333, MAF coded, changed MAF with OEM part. Light back on again, P1133--which is same code of part I just changed.

Any ideas?? Also, what is the difference in an A/F sensor and O2 Sensor? Are they the same thing or are they different parts?

I am increasingly frustrated that I have replaced high dollar parts and continue to get same codes as if parts never changed.

Thanks, Eric.  That's good information to have.  I spotted the driver's side oxygen sensor below the exhaust manifold yesterday.  It appears to be the easiest one to gain access to. 

With all the chatter I've seen on this forum previously about various sensors failing, I'm disappointed that more folks haven't participated in this particular discussion.  There are many out there who have already been through this, and they can teach us much about what the particular trouble codes point to.  All owners should bear in mind that once your vehicle reaches 60,000 to 70,000 miles, you're probably going to be dealing with these various sensor failures and you need to get prepared to do so.  The oxygen sensors alone cost around $210 each, and if you decide to pay a Lexus dealer to do the work, you will easily double or triple that amount for what should be a relatively simple fix.  Some of the other sensors are less costly  -  the Mass Air Flow Sensor retails for less than $100.  Many of these sensors are made by Bosch and you can order them from NAPA, AutoZone, etc. 

A crucial element of this entire subject is that a number of these various sensors are part of your vehicle's Emission Control System.  Certain components of all Emission Control System, regardless of make and model, are regulated by the federal government and therefore carry longer warranties than the basic 4 years/50,000 miles that Lexus provided for our particular vehicle.  Some of these Emission Control System components are warrantied for 70,000 miles while others are warrantied for 80,000 miles.  It is crucial that you read and understand your Lexus Warranties Supplement to your owners manual so you will be better prepared to deal with these various sensor failures which will undoubtedly occur if you keep your vehicle long enough.

I've had a running phone conversation with our local Lexus service manager since Tuesday.  Based upon our trouble codes of P01130 and P01135 (pulled at a local AutoZone, as previously reported in this post), they suspect the Air/Fuel Ratio Sensor (also known as the Bank 1 Sensor).  Our vehicle currently has about 69,400 miles, and the service manager finally agreed with me last evening that this sensor should not have failed this early.  She verbally agreed to diagnose it and replace the sensor at no charge to us as a "goodwill gesture".  My wife will drop the vehicle off at the dealership late this afternoon.  Once we obtain a diagnosis and a fix, I'll report that here.  In the meantime, those of you with RX300s may want to note that trouble codes of P01130 and P01135 indicate a failing Air/Fuel Ratio (or Bank 1) Sensor.

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[Dyllen]

RX in NC,

   There are three O2 sensors on the '99.  I'd assume it's the same for the '00 since very few changes were between those model years.  The '99 has one sensor just below each exhaust manifold and a third one just prior to the catalytic converter.  I am quite sure the front two are the exact same part.  The rear one is different however.  The front is the easiest to see as it's right under the hood downward of the exhaust manifold.  It is angled slightly toward the drivers side of the vehicle.

   Hope that helps.

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[Dyllen]

As skperformance suggested a couple of days ago, my wife had AutoZone read the trouble codes again yesterday afternoon after I cleared the codes in the morning by disconnecting the battery terminals for about 15 minutes.  One of the original codes from last week has disappeared, but the two remaining codes appear to indicate an oxygen sensor problem.  The question now is  -  which one?  This vehicle apparently has four oxygen sensors, and unfortunately they are not all identical part numbers.  I've called a couple of local independent service shops who specialize in Lexus and Toyota, and they haven't offered a solution that will allow me to nail down which oxygen sensor is creating the problem.  Our Lexus dealership just wants us to bring the vehicle in and drain our checkbook.

So what's next, guys?  I sure don't want to start guessing and wind up having to purchase all four oxygen sensors at about $200 a pop before I solve our problem. The remaining trouble codes are P01130 and P01135.

I've heard that some of these oxygen sensors are located before the catalytic converter while others are located after it.  Can anyone offer a clear explanation where all four of these sensors can be found, what they are individually called, and how you can get to them?

I'm also wondering whether specific preventive maintenance actions can help preserve the longevity of these seemingly fickle oxygen sensors.  With the typical RX300, they seem to start failing between 60,000 and 80,000 miles (we're just over 69,000 miles right now).  Do the various fuel injector cleaner additives or other component cleaners on the market add to the lifespan of oxygen sensors?   

As always, thanks for the assistance from those of you who have been through these battles before and paved the way for the rest of us....

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[alsalih]

I'm not 100 positive but P1133 is code for bank 1 O2 sensor which would be the one near the radiator. You need to know for sure which one is causing the code and replace it, I don't think it's the one behind the fire wall that is considered bank 2. Second, a recommendation for everyone out there, NEVER use aftermarket O2 sensors especially on Jap cars. The OEM sensors should be Denso and I highly recommend that you don't use Bosch as I have done this myself only to find the check engine light coming back. The outputs are not exactly the same as the OEM sensor and the computer doesn't like it. If you do it yourself you could buy them from www.oxygensensors.com or many other sites which carry OEM Denso sensors.

[danigirl]

I'm not 100 positive but P1133 is code for bank 1 O2 sensor which would be the one near the radiator.  You need to know for sure which one is causing the code and replace it, I don't think it's the one behind the fire wall that is considered bank 2. Second, a recommendation for everyone out there, NEVER use aftermarket O2 sensors especially on Jap cars. The OEM sensors should be Denso and I highly recommend that you don't use Bosch as I have done this myself only to find the check engine light coming back. The outputs are not exactly the same as the OEM sensor and the computer doesn't like it. If you do it yourself you could buy them from www.oxygensensors.com or many other sites which carry OEM Denso sensors.

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thank you for the info.

I work in the aftermarket arena. Bosch purchases their sensors from Denso and packages them in their Bosch box. I have been told this before when I owned my 4-Runner...same type issues with sensors from OEM only, however, you can look at the Bosch part and see the Denso name and part number on it?????

[zhoomer]

Believe we have engine bank location confused between several contributors which could cause you to replace the wrong sensor. 

Bank 1 (cyl 1,3,5) is located on the back of the engine next to the firewall.  Bank 2 (cyl 2, 4, 6) is

located on the radiator/fan side of the engine.  Standing in front of the car facing the firewall, the cylinder numbers start left to right, so #1 cyl is on the left (belts side) and next to the firewall.

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