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Cymro

Rx300 Mk 1 Oxy Sensor

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Having read with interest the recent thread about cleaning the MAF sensor on the RX300, Mk 1, I've just been told that I need a new oxy sensor. [That follows a dealer check after 2 warning lights (engine management and VSC) appeared]. The sensor costs £150+, plus fitting.

So I wondered whether, like the MAF sensor, the oxy sensor can be cleaned?

If so, where is it and how do I get at it to clean it?

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Having read with interest the recent thread about cleaning the MAF sensor on the RX300, Mk 1, I've just been told that I need a new oxy sensor. [That follows a dealer check after 2 warning lights (engine management and VSC) appeared]. The sensor costs £150+, plus fitting.

So I wondered whether, like the MAF sensor, the oxy sensor can be cleaned?

If so, where is it and how do I get at it to clean it?

after cleaning my MAF sensor I also cleaned the air intake to the fuel injection manifold. like a fool I started the car without connecting the MAF back up. I noticed the engine management and VSC were still on when the engine was running even after connecting the Maf back up. So I disconnected the Battery for an hour, the warning lights went out when I started it back up and the car runs perfectly fine. I don't know if you can clean the Oxy sensor but it's located at the top of the exhaust manifold behind the radiator. You can't miss it.

I picked up an Oxy sensor for my Audi A6 for £30 from local motor factors after having a similar quote from Audi. If you need to replace it, it's so simple a job it just unscrews after disconnecting the wires.

Hope this helps.

cnrke1

You didn't say whether you cleaned the MAF or the lights just came on.

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There are 3 sensors not just the one you can see. The 2nd one is not easy to get to being on the other half of the V near the bulkhead.

The first two sensors are also Denso air/fuel ratio sensors rather than just normal oxygen sensors so don't just buy a generic sensor, it won't work. Also if you purchase a generic sensor you will probably have to splice the wiring into the old connector.

The error code produced will tell you which sensor needs replacing and also what is wrong, e.g. heater faulty, no output, etc.

You can clean them but it normally doesn't make too much difference. To clean them you need to burn off any deposits gently using a blow torch.

For normal sensors they are easy to test by making the mixture lean/rich and monitoring the sensor output on an oscilloscope or some OBD-II readers.

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You didn't say whether you cleaned the MAF or the lights just came on.

Thanks for your helpful reply.

No - I hadn't touched the MAF sensor (a job for 'next week' again!). The lights came on at the end of a long run, when (without switching off) I stopped on a steeply-sloping drive [nose downhill] to let off my passenger, and when I moved off again on the level road, on came the 2 lights. The following day, after filling with fuel, the lights went out - only to return after about 15 miles and stay on. So then to the dealer, who diagnosed the oxy-sensor failure. It wasn't convenient to have the job done then. Of course, with predictable cussedness, in the last few days the lights have gone off again.... !

Thanks again for your reply.

May I also thank ColinBarber for his reply. I suspect discretion / timidity will prevail!

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I have some comments on the RX300 O2 sensors.... Only fit those available from TOYOTA/LEXUS. Why you may ask.... Well there's a lot of "useful" helper information on the 'net about how to test a sensor ( Ok you can read the OBD11 outputs, but that means you are spending money at a facility that has the instruments that can read this so it defeats the "money saving?) So NOT having access to the reader I read everything about how to test a sensor etc etc, and there is so much variation in the systems +1volt,+5 volt, inverted, don't do this do that, Oh and by the way none of it applies to a Toyota fitted with a TITANIA sensor, as they use 3.3V on both sensor legs and monitor the current flow, so of course a technician not in the know would condem the sensor anyway!!!

The sensors from Toyota are about £150 each, but you only need replace them once in a lifetime (if you are doing it more than that then something is seriously wrong anyway) The replacement of the correct item more than pays for itself in fuel savings, so whats the issue? As for fitting non Toyota parts I would seriously say NO WAY!!!. They aren't too expensive and copies do not always work in the same manner. My RX had a set of NKT copy sensors, which did not work the way the ECU wanted them to (Fitted by the previous owner who couldn't get the engine to run correctly, so I got it real cheap as a non-runner ha ha) Fit the correct sensors, clean out the IAC and EGR valves ( after you get the full set of gaskets from Totota) and enjoy another 100K on a correctly set up engine.

You have a BIG MANS CAR so PAY BIG MAN PRICES

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