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So in the attached image you can see the list of dtcs I have on a 2000 rx 300 AWD


I have tested coils and replaced spark plugs on 2-4-6, all should be in perfect shape.

I have tested unplugging the coils I could easily access with the entire intake assembled, which seemed to not affect the idle, leading me to believe that perhaps those spark plugs in the back are no good.


I am going to head back out now to work on getting to and replacing the 1-3-5 spark plugs, if I can manage. 


1. With the intake and throttle body(s?) removed, is it worth any attempt to remove the o2 sensor from above? I tried from below several times, with PB blaster let to sit overnight, to no avail.

2. As I was taking off the intake filter lid, I could swear that one of the two "vacuum" hoses directly behind it, may have been unattached. I followed the one that is attached and it seems to lead to the Fuel Injector rail for 2-4-6. With this logic, would it make sense that the other tube leads to 1-3-5 injectors, and all this could have been from the vacuum leak causing those cylinders to run lean/misfire?

3. Is there anything else I should check while I have the throttle body's off (and cleaned up beautifully) like the MAF, etc? I do have a multimeter, but I have only tried using it a couple of times and am not 100% on which items to check for which values.

4. Is there anyone here with any insight on what values to check on my Code Scanner's "Live Data"? I found a great OBD2 scanner, but I don't know how to use these tools to verify the fix...


My plan now is to replace the 1-3-5 spark plugs, reassemple the intake, verifying all connections are made and see how she runs... but I will work at the o2 sensor or anything else possible, while it's apart.


Thank you if you read this! I am new to the forum, as I just purchased this car for my wife, so thanks in advance, if anyone hears this!



rx 300 codes.jpg

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  • All spark plugs have been replaced.
  • swapped coils from 1,3,5 to 2,4,6. 
  • Replaced A/F B1S1
  • Still getting the A/F sensor CEL and Misfires only on 1,3,5 side.
  • I found that the Throttle Body's may need a gasket replacement, because spraying carb cleaner at it is effecting the idle, so those are next to be replaced.

I am now thinking of checking fuel to the injectors, injectors themselves, fuel filter...

Any other suggestions? 

If anyone knows the specific voltages and/or anything else that could help, please let me know!



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  • 9 months later...

yes! O2 sensor, new plugs all around, cleaned the intake.. Found that when I took off one of the gaskets, the other one wasn't there!

ordered the two gaskets for each throttle body, and it's been fine since!

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