New To The Forum - Maintainance Required Light On

[ULTM8Z]

Greetings, I'm new to the forum, but not new to cars. We have a 2005 Lexus RX330 that we bought used with ~39,000 miles earlier this year. Great car. However the maintainance required light came on a few days ago.

Being a gear head in my spare time, I know my way around cars (my hobby is a 1971 Camaro that I swapped in late model EFI). I have an OBD-II scanner, so I scanned the Lexus and no trouble codes were set. I did notice some curious things on the real time data and wanted to bounce it off you guys to see if there's an issue here.

1.) TPS sensor is reading 16% at idle with throttle closed. In all the other cars I've scanned, it typically reads 0%. I did step on the accelerator and the TPS % does increase smoothly.

2.) The scanner is able to read two O2 sensors. Though I'm not sure if the vehicle only has two. In any event, both O2 sensors were very sluggish in their responses, basically hovering around 720 mV... changing by about 10 mV every second or so. Again, on my Camaro, the O2 sensor bounces around quickly around a centering voltage of ~450 mV. If this were the Camaro, I'd conclude that something is pegging the exhaust into the rich zone or the O2 sensors are bad. Not sure if this is normal for Lexus

3.) Long term fuel trim is ~10%. That seems like a lot for a factory tuned car. I'm able to tune my Camaro to within 5% without a dyno or anything. The fact that this Lexus is off by 10% (combined with the O2 sensor data) leads me to believe there's some issue with the fueling???

Thanks in advance for your help

[steviej]

Are we talking the Check engine light or the Maint required light.

If it is the yellow icon that looks like an engine block then that is the CEL and you should be able to pick out codes in memory.

If it is the maint. reminder light then check to see when the last time the oil was changed. The newer Lexus models have a reminder light that flashes at 4500 miles when you start the engine and stays on steady at 5000 miles since the last oil change.

This is covered in your manaual. If you vehicle didn't come with a manual, I can tell you how to get one free.

Lastly, search on maintenance light reset or something like that. There are plenty of threads telling you how to turn it off. . . very simple.

steviej

[ULTM8Z]

Are we talking the Check engine light or the Maint required light.

If it is the yellow icon that looks like an engine block then that is the CEL and you should be able to pick out codes in memory.

If it is the maint. reminder light then check to see when the last time the oil was changed. The newer Lexus models have a reminder light that flashes at 4500 miles when you start the engine and stays on steady at 5000 miles since the last oil change.

This is covered in your manaual. If you vehicle didn't come with a manual, I can tell you how to get one free.

Lastly, search on maintenance light reset or something like that. There are plenty of threads telling you how to turn it off. . . very simple.

steviej

Thanks for the reply. Yes, the maintainance required light. I know how to turn it off, just want to make sure I'm not ignoring something important.

The data I retrieved and posted about above is still of concern since to me it appears out of the ordinary. How often to O2 sensors last on Lexus vehicles? I'd be hard pressed to think that both O2 sensors crapped out, so I'm wondering if something could be causing a rich condition.

[VBdenny]

The maintainance required light means oil change needed. It is easy to shut off.

As far as O2 sensors, my 1990 LS400 still has the original sensors and the car has around 175,000 miles.

[steviej]

Denso had a rash of AF sensors that were not very reliable. They were crap our short of 50k miles. These were seen alot in the 2002/2003 V6 used in the ES, RX, Avalon, Camry and other Toyo vehicles. Many people complained but Toyota did not do much except replace them under warranty. If you were out of warranty, then you paid. Supposedly they sensors have been improved and are more reliable.

That being said, I had one AF sensor go at 39k miles and one go at 58k miles on my 02 ES. My 06 GS has yet to throw a sensor and I am at 52k miles.

I sold my 02 ES with 108k miles on it and the O2 sensors in the it were still the original.

steviej

[ULTM8Z]

Denso had a rash of AF sensors that were not very reliable. They were crap our short of 50k miles. These were seen alot in the 2002/2003 V6 used in the ES, RX, Avalon, Camry and other Toyo vehicles. Many people complained but Toyota did not do much except replace them under warranty. If you were out of warranty, then you paid. Supposedly they sensors have been improved and are more reliable.

That being said, I had one AF sensor go at 39k miles and one go at 58k miles on my 02 ES. My 06 GS has yet to throw a sensor and I am at 52k miles.

I sold my 02 ES with 108k miles on it and the O2 sensors in the it were still the original.

steviej

Both sensors are saying the same thing... about 720 mV. Either they both crapped out and are stuck at the same value, or they're reading correctly a rich condition.

The other curious thing was the 16% throttle reading at idle even when my foot is off the accelerator. Not sure how Lexus PCM's work, but on my Camaro that would certainly cause an fuel mixture enrichment at idle speeds- which would certainly peg the O2 sensors into the high mV output.

I guess I'll have to see if I can find someone else's Lexus I can scan and compare the data...