Check Engine Light Came On Today....

[RX in NC]

I'm looking for diagnostic advice from those of you out there that have had experience with your "Check Engine" light coming on in the past.

My wife has a 2000 RX300 with about 68,800 miles on it. She called me this morning to say that the "Check Engine" light had turned on during her drive to work. My experiences with other vehicles tells me that a "Check Engine" light usually means that the oxygen sensor has failed or is about to fail. But I believe that this particular vehicle has multiple oxygen sensors, perhaps as many as three or four. What's the best way to diagnose this problem without going to the Lexus dealership and paying a huge price for what should be a relatively inexpensive part (if it does indeed turn out to be an oxygen sensor)?

Last October (while the vehicle was still under warranty), the "Check Engine" light came on and it turned out to be the Mass Air Flow Meter, which Lexus replaced at no cost to us. But we're no longer under warranty and can't afford to get hammered with a big repair bill right now.

I would greatly appreciate your experienced advice.

[dgorrie]

You really need to figure out the code that is causing the Check Engine light to come on. One approach is to visit your local O'Reilly parts store, or perhaps AutoZone or any similar, and "rent" their ODB-II analyzer. Many auto parts stores will effectively loan you the ODB-II reader that plugs into the connector under the steering wheel. Using that, you can get the code.

Start there, report back here, and I'll bet someone can help.

[SKperformance]

you must have missed my signiture

[RX in NC]

Thanks for the advice. My wife took the vehicle to a local AutoZone yesterday afternoon, and their diagnostic device spat out the following three codes and descriptions:

P0125 - "The PCM has determined that the amount of time it took for the coolant temperature sensor to reach an input value consistent with closed loop operation was excessive."

P1130 - "Lack of HO2S Switch - Adaptive Fuel At Limit."

P1135 - "Pedal Position Sensor A Circuit Intermittent."

The AutoZone tech then used his diagnostic device to turn off the "Check Engine" light. Within a mile of my wife driving away from AutoZone, the light came on again.

I'm not convinced that AutoZone's diagnostic gear is always accurately calibrated for every make and model. These three codes and descriptions don't seem to be related to any specific condition - one mentions coolant temperature, one mentions fuel, and one mentions pedal position. Can anyone out there make any sense of this information?

Reading the owners manual last evening, it states that if you do not sufficiently tighten the gas cap after purchasing fuel, the "Check Engine" light will turn on and it may require several driving cycles before the light turns off again. My wife bought gas the previous evening but I've always told her to close the gas cap until she hears at least three clicks and she claims that she always does this. I removed and re-set the gas cap, generating at least six clicks before I stopped turning. She's back in the vehicle today and we're going to watch it for a couple of days to see if the "Check Engine" light turns off again.

I would appreciate any explanations of the seemingly unrelated codes that spat out of AutoZone's diagnostic device. The tech believed that the problem probably occured from a loose gas cap. But I'm not so sure about that yet.

[SKperformance]

you have 3 problems

now that you have codes something can be diagnosed alittle.

the tool autozone has is just a code reader ,nothing like an anlyzer

the tool just shows you codes that the computer gives it.

the light is only reset but if the problem still exists it will come right back on .

you have a

[RX in NC]

I seriously doubt that we have three very different, unrelated problems that all showed up as codes at the exact same time when the "Check Engine" light came on. I really question the accuracy of AutoZone's diagnostic tool.

This may still turn out to be a gas cap issue, but the codes continue to concern me.

Can anyone else out there make sense of this information? Thanks for your assistance.

[RX in NC]

After reading through some of the previous RX forum posts dealing with the subject of "Check Engine" lights coming on, I've decided to clean the Mass Air Flow Sensor with Gumout Throttle Body Cleaner and a can of compressed air. This could be an easy and inexpensive solution to our particular problem. I'll report back later to let you folks know whether this made any difference. With Hurricane Charley bearing down on the East Coast now, it may be a few days before I get to this task.

If anyone else has further suggestions concerning my situation, please post here. Thanks.

[oldrx300]

Where is the Mass Air Flow Sensor? I looked around the forums but it's not clear where it is or what it's look like.

[RX in NC]

The Mass Air Flow Sensor is located on the outside of the rear of the air cleaner plastic housing. Look for a small tube-like assembly with hoses and an electrical connection.

I obtained a can of Gumout throttle body cleaner spray and a can of compressed air over the weekend and will be cleaning our RX300's Mass Air Flow Sensor by mid-week if all goes as planned. I noticed that the directions for using the Gumout throttle body cleaner spray state in capital letters, "DO NOT SPRAY THROUGH AIR FILTER OR ACROSS MASS AIR FLOW SENSOR". What's the risk, folks? Saturating a paper filter? Causing electrical sensor problems? Surely someone out there can explain the risk as well as the proper way to carefully perform this procedure....

[SKperformance]

the ecu stores codes until they are erased

if it is intermittent or has happened befoer you owned the car it will remember them.

so it doesn;t mean you have 3 codes but at some point in time you did

go back and get them to read it again to see what troubles are still there

[RX in NC]

skperformance,

Good idea, but I still question the accuracy of AutoZone's generic code-reading device across all makes and models. Do you trust it to be accurate?

[oldrx300]

I think this is the Mass Air Flow Sensor, can somebody confirm this?

Thank you.

[RX in NC]

I agree - that looks like the electrical connection for the Mass Air Flow Sensor.

[RX in NC]

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....

[eric618]

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.

[RX in NC]

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.

[oldrx300]

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.

[RX in NC]

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.

[Unlisted]

Generally if an item is diagnosed under the warranty period or you mentioned that is wasn't working at the time and wasn't repaired, most dealers will cover after the warranty period

[brandondiem]

I had to replace my o2 sensor back in late June- My RX300 had about 56k. With no time to delay I had the dealer take care of it- Cost me $400. Hopefully the other sensors will not crap out anytime soon.

[DimoGen]

I had to replace my o2 sensor back in late June- My RX300 had about 56k. With no time to delay I had the dealer take care of it- Cost me $400. Hopefully the other sensors will not crap out anytime soon.

We are close to 95K miles now and got identical problem with Air Fuel Sensor. Dealer wants to replace for $480 + tax. I guess I will go for it. But my question to 'Brandondiem" and others is how long does it take until the next time the sensor goes faulty. I just think that if I have to replace sensor twice a year or more often I might better get rid of this car. Did anyone have to replace sensor more than once?

P.S. Also great thanks to RX in Nc for this detailed topic. I basically got more answers here than I got from my dealer.

Cheers

[lexus_romeo]

At 59k had to replace O2 sensor (Bank 1, etc, just as described above), covered under dealer/no charge warranty. 99RX300_AWD

[APN]

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.

OLDRX300 :

How did you clean the MAF, can you please share ? I replaced my A/F sensor (bank1) but still have the error (P0171 - system too lean bank 1). My next step is the cleaning the MAF.

I also found and fixed the problem with clock reset when engine is started if anyone interested.

Thanks

APN

[Phil E]

I've been following this topic for a while since my check engine light came on. Per the advice of some of the posts, I went to Auto Zone and their portable code checker displayed "P0172 system too rich." The salesman then recommended that I add "STP Jet Fuel" to my gas to clean the fuel injectors. I went ahead and bought a bottle of the stuff but haven't done anything with it yet since I seem to recall varying opinions about fuel additives. I have noticed I seem to be using more gas than normal.

Has anyone had any experience with either this trouble code or this fuel additive?

Thanks for sharing.

[RX in NC]

I'm not familiar with that particular trouble code, but please keep us posted as you learn what component it points to. Perhaps others will jump in here if they've experienced your particular trouble code themselves. You should call your local Lexus dealer, speak to the service manager, and attempt to get him/her to tell you more about what your trouble code means. Some will, some won't. But you won't know unless you try.

I believe that good quality fuel injector cleaners are money well spent on an occasional basis. Unlike most oil additives which are all about hype and convincing you to part with your hard-earned money, tests have shown over the years that fuel injector cleaners usually accomplish the purpose they are designed to perform. The best news is that they are very inexpensive. Go ahead and pop that bottle in your tank and see if it makes any difference for you.