acbjj5

Newby poster to this forum. Read many posts over the last year an appreciate your past help. Sorry about long 1st post. My issue is in 2000 RX 300 AWD. Bought car needing a motor and put in a used motor. Got a CEL with a lean code on Bank 2, although I felt it was running rich due to exhaust smell. I put a new fuel oxygen sensor on Bank 2. Car ran great with no CEL for a few days and then CEL returned with lean code on Bank 2 again. I then borrowed a code reader with data feedback. Short Term and Long Term Fuel Trim numbers were very lean on bank 2 at all rpm’s. I then removed the sensor, which had a lot of carbon build up. I cleaned and swapped the sensor with the Bank 1 oxygen/fuel sensor. The lean problem then moved to bank 1, following the new sensor. I then did a return on the oxygen sensor and put the new sensor #2 back on Bank 1. Watching the fuel trim numbers at start up, initially, the sensor showed lean, but started functioning properly once I rev’ed the engine. I took car for a long drive and fuel trim numbers very good until near the end of the drive where bank 1 started showing lean (19) at idle. Daughters drove for few days and CEL returned. I then removed sensor and cleaned carbon buildup with small amount of heat and blowing air. I then re-swapped the cleaned new sensor #2 to bank 2. (If I continue to have problems, I want to deal with bank 2). I started the car and fuel trim numbers were good at all rpm’s for about 5 minutes but did not test drive. Next time I started the car, several days later, bank 2 fuel trim is 19 (Lean) and did not change at any rpm. My question, is this still an oxygen sensor problem or is there something else I should check. I bought the sensor off ebay. It is an OEM sensor, but not bought from dealer. Part # 89467-48011, came in a Toyota OEM box. Before spending big $$ for dealer sensor, just want to be sure I am not missing something? The way the lean code follows the sensor, you would think that would be the issue?? Odd the way the car functions properly for a while and then turns lean. Any help appreciated.

ukrkoz

yeah. You mentioned is three times I believe.
Carbon buildup. WHY is it building up carbon deposits in exhaust so fast? And what exactly is carbon build up?
https://www.google.com/search?source...k1.0ZOmzLvOadw

acbjj5

I think the carbon buildup is from the sensor giving a false lean condition and the computer adjusting creating a rich condition.The sensor functioning properly has very little carbon buildup.I will add that the sensor that is working does not have the Denso 89467-48011 part number.The one I initially replaced did have this same part number.The functioning sensor is a Denso 192400-8070 with the number 01025 under that.I have done searches and that part number is not available.I wonder about PCM communication with the sensor.I have read in this forum about software updates to the PCM, but there is very little information that I could find on the subject. I could be off base on that being the potential problem??

maxSteel

You should watch this video
https://www.clublexus.com/forums/rx-...uel-trims.html

acbjj5

Thanks for the link, video has very good info. on Fuel Trim.

acbjj5

Just an update. I bought another fuel/oxygen sensor from a local dealer and installed tonight. So far, fuel trim numbers are good and car is running good. Hope and pray that problem is fixed. Will try to post again in a few days if fuel trim numbers remain good and CEL stays away.

Drcoffee

Have you checked the routing of the vacuum lines on the evap system. My rx300 had the trans replaced and I assumed it was installed correctly. It turns out the mechanic had the vacuum lines connected wrong. And the gas cap was leaking and all that was causing a lean condition. There is a chart for the hoses.

maxSteel

In that video he says if you replace oxygen sensors for a system too lean code you're an idiot.

He explains why your numbers will be fine for a while after you start - the oxygen sensors don't work until they heat up.

He also explains how to differentiate a vacuum leak from another cause.

In my case the cause was a bad MAF sensor. I had tried cleaning it first. I also checked with an ohm meter, it failed one of the resistance tests.

acbjj5

It has been several days now of driving. Fuel trim numbers are still good, vehicle is running good, and no CEL. I am starting to think it is fixed. Maybe the moral of my story is be absolute certain that what you are buying is a genuine toyota/lexus part. I bought the first sensor off eBay from a seller with excellent feedback. Sensor had the correct OEM part number and came in a toyota box. The replacement the seller provided was the same. It just did not work. Dealer sensor I purchased looked identical with the same box as the sellers off of eBay. Only exception is that it has been working. I have read in this forum about the online lexus parts outlet, I could have saved a little money using one of those suppliers, but felt more secure buying from local toyota dealer. Thanks

artbuc

You do not need to spend big bucks for OEM A/F or O2 sensors. Aftermarket Denso's are very high quality and will work great at much lower cost.