Still Having Probs With 02 Sensor

[bluetoy]

Hi Guys, sorry to be a pain but as I have posted 2/3 times this week I am still at a loss. To recap. I have replaced the 02 sensor on my 1998 avensis 7A-FE engine. The engine was running rich and the garage diagnosed the fault to be 02 sensor faulty. On replacing the sensor I drove about 12 miles and the eml came on . I took the car to the garage again and they diagnosed the 02 heater circuit faulty. I returned the part and got a replacement. Again the light came on after about 12 miles (please note when the old unit was refitted there was no light on) I carried out the pin test with the paper clip and it is showing code 21. I have read the articles on here and that signifies a sensor failure again.. the car runs ok. On questioning the motor factor he said there must be something else wrong with the car. Can anybody tell could there be a fault in the system that would cause the heater circuit to fail on the 02 sensor or is there anything I can check to ensure there is not? I cannot get away from the fact that the light doesn't come on with the old sensor. I have also tried to find a tester/code reader for this car but unsure which protocol is being used. Don't know if it has obd1 or obd2. Can anybody advise?

Any help would be appreciated

[talldave]

I have the same car as you. I replaced my 02 sensor a couple of years ago with a genuine DENSO one from www.gendan.co.uk. It cost £146 instead of the £416 that Mr T wanted. How much did you pay? Are you sure it is the correct one for the the 7A-FE lean burn engine. If it cost much less than I paid then I suspect it may not be. I recommend getting one from Gendan.

I don't think you can get an ODB reader for the 1998 Avensis. As you say you can use the pin/paper clip method and yoiu have the same code (21) that I had. This means "Oxygen Sensor".

[bluetoy]

Hi Dave,

It was a blueprint sensor fitted, Cost over £90. Was recommended by local garage as being quite good as he has fitted lots of them and has never had a complaint. The thing is ... if I put the old one back on... the light don't come on. Runs ok with new one but the light keeps coming on. The factors are willing to take the part back but wont exchange it as they reckon there is something else wrong with car. Maybe I should take it back and get a refund and go for Denso.. But I fear that the light might come back again.

Thanks for advice well appreciated

[talldave]

If you can return the blueprint sensor and get your £90 back I would do that and then get a DENSO one. OK its probably another £50-£60 but worth it I reckon. My approach is to always use genuine parts if possible. As you say, when you put the original sensor on, the engine management light doesn't come on, with the new one it does. To me that suggests that the new one is not compatible. Good luck.

[waqar_lionheart]

having changed a few on my car, I reckon your new sensor is knnnnnnnnnnnnnnnnackered. Sorry dude but i think it is.

Regards,

Waqar

[Devon Aygo]

The 7AFE engine was available in two forms, they varied around the fuelling and emissions systems fitted, one engine was considered normal the other was equipped with a "lean burn" engine. The exhaust sensors from each engine look physically similar but operate in different ways. it is possible that you have a normal sensor fitted to a lean burn type or vice versa the outcome being the engine ECU will set a fault code.

PM your chassis number and I will confirm which system you need

[bluetoy]

Pmd now Lee hope you can throw some light on subject.

[Konrad C]

The 7AFE engine was available in two forms, they varied around the fuelling and emissions systems fitted, one engine was considered normal the other was equipped with a "lean burn" engine. The exhaust sensors from each engine look physically similar but operate in different ways. it is possible that you have a normal sensor fitted to a lean burn type or vice versa the outcome being the engine ECU will set a fault code.

PM your chassis number and I will confirm which system you need

Add the auto variant into the mix. I was going to get one ( Denso) as mine throws an EML occasionally. The part numbers did not match and then I found out that it was for an auto. I didn't buy it.

I am still using my Denso sensor as car runs well and the light only comes on for a few minutes then goes out. If I switch off then on, the EML stays off. The emissions are good and I am still getting 450 miles between fill ups. The light is mainly off so I don't worry about it.

[Konrad C]

having changed a few on my car, I reckon your new sensor is knnnnnnnnnnnnnnnnackered. Sorry dude but i think it is.

Regards,

Waqar

Waqar,

I think you're right about the original sensor. The second may not be fully compatible as mentioned by Lee.

Lucky the Lean burn only has one sensor, so there is no guessing which sensor needs changing.

I will only buy Denso because the system has to match, if that makes sense.

Thanks Dave, I now know where to purchase my next sensor (Gendan or Euro Car Part). I am not sure if the place - Nippon Automotive are still in business. That's where I got my replacement, 6 years ago. The price is fine.

Konrad

[Konrad C]

In your other post, others and myself have mentioned sources for obtaining original Denso sensors.

Now since you have the pre vvti engine, do the "paper clip" trick to get the EML code. That is how I get fault codes for my car.

By jumping pins 4 and 13 on the OBD socket, turn on key to ignition and you will see the EML, ABS, and SRS lights flash. When the EML flashes twice space then once, it is code 21 - O2 or leanburn sensor.

The above is for those with pre- vvti engines that cannot use code readers.

Also there are variations of the sensors for the leanburn engine, auto and manual.

Konrad

[bluetoy]

Carried out this test Konrad. definately code 21 flashing. Factors now refusing to change the 2nd sensor unless full diag carried out on engine. Once engine recycled car can do about 10/12 miles b4 light comes on. seems the light comes on when car in overrun condition. i.e slowing down when lifting foot off throttle pedal or coming up to a junction) It always seems to happen at the same mileage. when engine recycled the light goes out and stays out for another 10/12 miles. Now my head is full of scenarios thinking it could be throttle potent sensor or air mass sensor. Cant get over the fact the old sensor never brought light on but have been told by tech guys that as your old sensor was faulty it could have been masking an underlying problem???? Yeh but what???. Seems unless I replace sensors trial and error style or pay Mr T for a full diagnostic I will never get to the bottom of it. On the other hand I could Shell out the £150 for a denso and have the light still come on. catch 22 it seems

[Konrad C]

Bluetoy,

Some garages not just Toyota can do a diagnostic check on your car. You need to ask.

The Toyota self test is fairly accurate and code 21 means the sensor is the problem. Make sure the wires to the sensor and the connections are okay.

The other way around your problem, which will be difficult, is to meet somebody with a similar car and temporarily swap sensors to see what happens.

Another also difficult option would be to find a scrap or secondhand sensor, but there may be a risk of it not working.

Personally I think the Factor you bought your sensor from is being unreasonable. If I had a problem with a part that was not the genuine article, I would want a refund to buy the genuine part.

I think Euro Car Parts sell the Denso version. Best check with them first if they do, and what returns policy they have. Their price is £150 if you order online.

Now if the Denso sensor works and you have no problems, then that should be good enough for you to get a refund for the other sensor.

For a benefit of other reading this, The part must be fit for purpose on the car it is being used with. If any warning lights show, and that part is the cause, then it not fit for purpose. Also I think it may be a problem for the MOT.

Have you checked other parts of the engine, like vacuum pipes, electrical connections? You mentioned the 'throttle potent sensor or air mass sensor'.

​Also check the inlet valve linkage. This system shuts off 4 of the valves at low engine rpm, promoting a high swirl in the combustion chamber for the lean burn to work. When the engine speed is high enough, the inlet flap control opens the 4 inlet valves.

This is known to detach so 4 of the inlet valves are not getting the right flow. The car does not run properly.

Check the HT leads. If they are not genuine Toyota leads, they may not be plug firmly onto the spark plugs. I tried two sets and they cause lots of issues, especially when the car had warmed up. Cheap petrol seemed to cause issues when using the faulty HT leads. I am back with the original Toyota leads that came with the car with no problems.

I have given as much as I can given my experience from my own car. Read my posts.

Konrad

[waqar_lionheart]

I have a 2001 1.8 vvti. I have had my fair share of o2 sensor probs and managed to fix them all by myself.

I am not sure what code 21 is, for my car has obdII compatibility and code are quite specific to condition (its good and bad at the same time as good because gives a v good idea of what the prob is, bad because little things bring up eml. Anyways I digress).

O2 sensors are subject to engine temp, cat temp and most importantly your o2 sensor's temp. your code description is heater circuit malfunction ( i googled this) which means that your o2 sensor isnt heating up to right temp for it to start communication with ecu and make adjustments to fuel trim. It only means that your car runs in open loop(rich as in the old days on choke; well kind of) until your o2 temp rises to the right temp. I am given to understand its v high. This is achieved as the car is driven and the sensor gets hotter and hotter (same principle as CAT only operates at the right temp but this temp is achieved by engine exhaust heat). So in essence, the only problem you have is that your sensor is working fine but you are not getting data from the moment you turn your engine. The sensor just waits until you get it to the operating temp by driving the car for a few miles until the engine is fully hot and then some.

So coming to MOT if you drive your car and get it to the temp before you take it for a test and then when the car is idling it should be alright.

Any probs, give me a shout(email or reply on this forum). :)

Regards,

Waqar

[waqar_lionheart]

I would say one more thing, these sensors are generally blown by age factor (number of miles the car has done) or if you are running rich. If a car is running rich it leaves deposits on the sensor element which prevents it from heating up properly and then BANG the light comes on. I wouldnt worry about it at all, its a shame that your sensor isnt working, I think thats down to the type of sensor you might be using. You have to get the original one. thats best.

[Konrad C]

Hi Waqar,

I will tell you what code 21 is, and how it can be done on pre vvti cars made before 2001. You car is EOBD compliant, so can use EOBD/OBD2 fault code readers. The 7A-FE, 4A-FE & 3S-FE engine are not EOBD compliant so cannot use the readers. What can be done is the 'paperclip' test. I use a copper wire to link terminal 4 and terminal 13 on the OBD socket. Then turn the key ignition. What happens is the EML, ABS and SRS will flash. In the case of the EML with the O2 sensor fault, it will flash twice, short pause then flash once. There will be a much longer pause then repeat the flash sequence. This is fault code 21.

I have added the following pictures:-

I recorded the flashes, but need to upload the video later so you can see what is happening.

When we next meet, I will show you how the test is done.

You can do the same test but only the ABS and SRS will flash.

The best thing is that it practically free and saves on buying a reader that would not work on pre 2001/non vvti cars anyway.

Konrad

[Konrad C]

Can I add that I had ABS fault codes flash too. Codes 33 and 34 when Googled is both rear wheels. I actually triggered the fault last year when trying to trace front wheel bearing noise, with the front wheels up on axle stands. I can't remove those stored codes unlike the EML. Actually it could have been when the transmission was test during repair.

[Konrad C]

Hi Waqar,

I will tell you what code 21 is, and how it can be done on pre vvti cars made before 2001. You car is EOBD compliant, so can use EOBD/OBD2 fault code readers. The 7A-FE, 4A-FE & 3S-FE engine are not EOBD compliant so cannot use the readers. What can be done is the 'paperclip' test. I use a copper wire to link terminal 4 and terminal 13 on the OBD socket. Then turn the key ignition. What happens is the EML, ABS and SRS will flash. In the case of the EML with the O2 sensor fault, it will flash twice, short pause then flash once. There will be a much longer pause then repeat the flash sequence. This is fault code 21.

I have added the following pictures:-

P1020854.jpgP1020853.jpg

I recorded the flashes, but need to upload the video later so you can see what is happening.

When we next meet, I will show you how the test is done.

You can do the same test but only the ABS and SRS will flash.

The best thing is that it practically free and saves on buying a reader that would not work on pre 2001/non vvti cars anyway.

Konrad

I have now found a way to upload a video showing the EML flashing the fault code.

My first video which I hope will be helpful with the photos showing the jumper wire in the OBD socket.

Konrad

[Edwardius]

Can I add that I had ABS fault codes flash too. Codes 33 and 34 when Googled is both rear wheels. I actually triggered the fault last year when trying to trace front wheel bearing noise, with the front wheels up on axle stands. I can't remove those stored codes unlike the EML. Actually it could have been when the transmission was test during repair.

Konrad, you can clear ABS codes by depressing the brake pedal 8 times in 3 seconds with the ignition switch turned on.

[Konrad C]

Can I add that I had ABS fault codes flash too. Codes 33 and 34 when Googled is both rear wheels. I actually triggered the fault last year when trying to trace front wheel bearing noise, with the front wheels up on axle stands. I can't remove those stored codes unlike the EML. Actually it could have been when the transmission was test during repair.

Konrad, you can clear ABS codes by depressing the brake pedal 8 times in 3 seconds with the ignition switch turned on.

Thanks Ed,

I found out earlier and posted the fix myself. I am sure there are more secrets to be found, but Pete says I must get out more, which I agree with the nice weather right now.

Konrad