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Check Engine Codes


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Hi guys/gals!

My gas milage is down to about 11mpg (from 17) and I got the following OBDII codes:

(All P) 0300, 0301, 0303, 0305, 0171, 0174, 1130, 1153

I'm hoping that by by replacing the two O2 sensors (based on 0171 and 0174) the other codes will be fixed. However, I'm not sure of the following:

1) Where are those two sensors located (I think I have 3 sensors total on this RX300)

2) Does anyone know the part numbers. I've heard the Highlander is the same engine, so I was thinking of trying to get them from the Toyota dealer near my home

3) Are they difficult to replace (as always pics, instrcutions would be apprciated).

I am also polanning on cleaning the MAF sensor, but I already have instructions on that.

Thanks in advance!

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The po300 codes indicate missfires, You may have bad plugs or Coil packs. there are three sensors, one on each side of the engine near the exhaust manifold. You can see the front one near the radiator fans. the back one from under the car and the third one just before the final catalytic converter. They are not cheap. I would go after the missfires first. this could be causing your other codes. looks like cylinder 1,3,5 have a problem. those are the back three cylinders. You could try and check the rear sensor, the two black wires are the heater, make sure they do not measure and open with an ohm meter. If they do, both the front and rear sensors will not have a heater they are wired in series.

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Thanks! Not to be to dim, but sounds like changing the plugs would be a good first step. It's time for it anyway. I've heard using the NKG is best?

I haven't looked in my owner's manual yet, but does yours give the OEM spark plugs? I ask because my Acura listed two different but acceptable plugs. I chose to replace them with what was in there. I believe that, if you do a search, you will find the front plugs are easy to do (no kidding?) but the rears are time consuming. There was an article with a DIY plug section in it.

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