2000 RX300 AWD -- 109005km

Check engine light came on tonight. Before winter started we had some idle and stalling problems but they "stopped" after we replaced the battery. A few nights ago I was on an decline idling and the RPMs were fluctuating between 500-1000RPM, sounded like the engine wasn't able to breathe. I drove away to get the RPMs back up again. I don't know if that has anything to do with the CEL but every bit of info helps. There are no other noticable problems with the vehicle.

Does the CEL come on for regular scheduled maintanence intervals? Or does the CEL come on only when there is a problem?

My guess at this point would be an O2 Sensor.

Any input would be great!
Regards

 

The CEL only comes on for problems. May be just the idle air control valve needs cleaning. I think if you take it to the dealer they don't bother cleaning, just replace. If you have a Autozone around they will read the code for free. Then come back with the code and do a search both here and at Lexus owners club. You can get a good idea of what needs to be done.

 

Update:

Dealer found a trouble code: P0171
Replaced the O2 Sensor at $221.40 for parts and charged 1 hour of labour. NOT covered under warranty.

 

Wow, the P0171 System too lean is related to the Air flow meter on top of the air filter housing, not the O2. If the CEL come back, you tell your dealer please look at Short and Long term fuel trim in the data menu on the scan tool.

 

that's actually not an o2 sensor. It's a Air flow sensor. Looks like an O2 sensor but it isn't.

 

Same code was just triggered in my car yesterday. Took it to AZ and they told me P0171 and P0174.

 

I am 7,700 feet with about 25% less oxygen than at sea level. Whenever I get a check engine light down here, I always place a bet with my mechanic that it is a P0171. We get out the OBDII scanner, and I am always right. One time it was K&N gunk on the MAF, but occasionally I get a low idle in certain parts of the year or under certain conditions, i.e., after a 3,000 foot drop I sometimes get vapor lock.

The new mods I have with regard to greater air flow help incredibly, especially when going up hills, but at sea level I would be just fine.

Usually, there are other codes that would indicate which bank of O2 sensors had a problem, but I have never been affected by that.