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O2 Sensor Prob


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lexus is200 se auto 2001

Hi all

Recently my engine manegment light had come on, so i got a mechanic to read the fault code which come up as: o2 sensor bank one. It did not come up with anything else. I was told that sensor is the 1st one on the manifold downpipe. Got it changed with a universal o2 sensor where the wires had to be soldered together to fit the old plug. This has been done correctly. Then the ecu was reset by the Battery terminal. After driving 10miles or so the engine mangement light has re appeared. It does not flash, just stays on. Hope iv provided enough information, any feedback/advise will be brilliant. Thank you.

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You will probably need to read the DTC's again, and it will probably show the same code.

Some of the universal o2 sensors are tricky enough to get right, check with a multi-meter to be sure that the Signal wire & heater wire are the right way round,

Some older cars have an o2 heater relay and fuse and also won't power the sensor while a code is present.

so first off you need to clear the code, check the heater ground and supply, if no ground you have faulty wiring, if no power posibbly relay or fuse or faulty wiring.

Hope that this helps

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Thanks JollyRoger

I got the car diagnosed this morning. It read the same problem bank 1 oxygen sensor.

The wiring has been re checked and it is all correct. There are two heater wires with the

original sensor, and the universal sensor wires up either way round (according to the instructions)

then 1 to ground and the other to the ecu. I have been told that aftermarker/copy or universal

sensor's will not work on this car. So i will need to purchase it from the dealers.

Unfortunately they are closed now so ill need to wait until Monday. Hopefully it will reslove the


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Hi all

got the same problem exactly, however screwed the thread when I tightened in the new after market copy so removing it and changing it could be a real problem. Will also try and check the codes and follow the advice above. The Toyota lexus dealer said that if I tell him the codes he would check it out. Apparently if the front o2 Lambda sensor shows a fail, it could also mean something else is at fault and he would advise me.

Bobby the fish

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Yes you will need to be careful removing it, if it happens to break you can stock and dye

the threads to remove any deposits,

I have been to my local lexus dealer and been quoted £204 for a Denso o2 sensor which is not what i expected,

Iv located another Desno o2 sensor for my IS200 of eBay, direct plug in £62

This is the only problem showing on the diagnostic, so i have ordered it and hopefully it will do the job.

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  • 2 weeks later...

Finally got my denso o2 sensor delivered and fitted yesterday (bank 1 sensor 1)

After driving the car for 10 miles or so the engine management light is back on.

Got the code read, again it's coming up as o2 sensor bank 1 sensor 1.

The code is P0420......

Surely it cannot be the sensor again as iv changed it twice

The car does seem to be quite thirsty on petrol,, any idea's ??

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  • 2 years later...

It sounds to me like they have come to the wrong conclusion about the code. P0420 is "Catalyst System Efficiency Below Threshold (Bank 1)" which tends to mean that the readings before and after the cat (from the pre and post cat sensors) are too similar to show that the cat is being effective. It would normally point to the cat being buggered or a leaking exhaust. The codes for problem O2 sensors would generally be in the P01xx range IME.

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