Has anyone tried to test the sensors what type of resistence/ voltage should i be reading? & which wires? thanks......

 

Welcome to the Club

https://www.clublexus.com/forums/rx-...esistance.html

 

Honolulu, unless I'm mistaken, a simple test of continuity should actually be sufficient since those 2 wires (should be 2 black wires) are simply on or off for the heater. They have nothing to do with the actual sensor, only the heater. They don't (or shouldn't) even operate very much of the time. The higher ohm rating at the higher temp. is also normal, higher temp, higher resistance. From what I also seem to remember, the ohm rating in the factory manual is incorrect. Artbuc bought a new (or had installed) A/F ratio sensor for his deceased RX because the old one was out of range and found the new one to be in the same range. I believe they took the new one back and apologized for the error in the factory manual. (I have a factory manual and have found errors in it) The car will run quite normal for the most part, with a bad heater in the A/F sensor (it is only on for a VERY short time when cold to bring the vehicle to quick "closed loop" and when coasting down a long hill or similar, when the exhaust cools excessively, the rest of the time it's just along for the ride (the heater part, that is). I've had experience with this and was assured by several Lexus techs that it wouldn't hurt anything to drive it that way.

 

Roger, that happened on an IAC valve which was much more expensive than an A/F sensor. The factory Repair Manual showed electrical troubleshooting specs for an analog IAC valve like the one in my 99 Avalon. The 99 RX has a digital pulse type IAC valve which can not be checked electrically, at least not with a VOM. It took several phone calls but I finally spoke to a regional technical maanger who seemed to understand the problem. They said they would correct the repair manual but I don't think they did. I did get a full refund which was around $230.

Also, as I recall, the wiring is mislabeled in the MAF electrical troubleshooting section. The actual electrical checks are valid once you figure out the correct wiring.

 

Sorry about that Art. My 'memory mistake".
Interestingly, when I 1st worked on the RX, I had NO knowledge of them at all, so it was a "CRASH" learning course for me, since I had a deadline for when the RX was heading for Seattle for an extended period, and a LOT to do. I removed and cleaned the IACV, re-installed and it worked perfectly. While I was working on some of the many other things I had to do, I decided I didn't want my DIL to have any kind of problem, so I ordered and installed a new one after all. I tested the original that now worked perfectly and found it to be WAY out of specs, I believe 2ohms one direction and 59ohms the other direction. I tested the new one (OEM) and found it not to be very close to what is called for in the manual- 17-24.5 ohms, cold. Went ahead and installed it because time was short and over 50k mi later it still works flawlessly, but the the original did also after cleaning when it was off drastically in the ohms test. ??? If someone can figure that one out, please let me in on it. Evidently the fact that the Ohms test is invalid on that IACV.

The car was in Seattle when the CEL came on and showed the A/F ratio heater bad. At least the info I posted on that is correct.