New O2 Sensors

[princess]

I posted here about the management light on my dash. My mechanic ran a fuel cleaner through the engine and he has also cleaned the sensors etc. The filters were all new as it jsut had a service. He said he has done everything he could and it's still no better (the car is also running really sluggish as well as the light being on) and I need new 2 new o2 sensors at a total of about £280 :o

Is there anything else he could try, or is it likely that these sensors really are necessary?

Also worth noting is that when i got the car back after the service it felt slightly more sluggish, but i thought i might be imagining it. It got gradually worse after the light came on. He says he used all original parts for the service.

Please help, really can't afford this cash, bought a Yaris because it was supposed to be cheap to run and never go wrong - I haven't had it a year yet!

Edited to add, I've just done some more reading and read that a failed o2 sensor will cause unacceptable exhaust emissions and failure of the cat as well as decline in fuel economy. There has only been a 2mpg decline since the last time i had the car back and that's with me doing more driving in bad traffic and less on good roads. At the same time as the service it was MOT'd and passed fine on emissions. Does this mean it's less likely to be the o2 sensor?

[jaxx]

try contacting these guys

http://www.oxygensensors.com

mite need a bit of info on the type of engine/sensor as its a US site, but you should save a few quid

also are they sure both of them are shot? mite be worth getting one and trying it in both positions before shelling out completely

then again the cat may have had it and your just getting bad readings due to that and theyre really fine!

[princess]

HOw can I find out the part number for the sensors? My mechanic says he called toyota and they won't tell him the part number and he doesn't know it! Am going to try some breakers yards out of desperation...

[jaxx]

which yaris have you got? year/engine etc......

[princess]

1.0l 2000/W reg GS model.

Is this something you might find in a manual/Haynes book, or is there somewhere else you can check these things?

[jaxx]

it wont be on the Haynes book trust me

ill have to have a look in my parts manual to try and find out....

but if you look at this

http://www.automedicsupply.com/catalog.php...;engine=L4-1.5L

its stated for the 1.5 engine, unsure if they use the same ones? (anyone?)

theres also the option of using universal sensors which will require a bit of jiggery with the wiring (nothing complex, just a + a - and a sense wire) and thatll cost you about 30 quid per sensor

[princess]

Cheers, link doesn't work for me though.

Do the universal ones work the same as the originals - as in are they as good quality?

[Bee]

Do the universal ones work the same as the originals - as in are they as good quality?

This one is selling non-OEM diret replacement oxygen sensors and universal oxygen sensors.

http://www.gendan.co.uk/article_11.html

The direct refitting unit for 2000 Yaris appears to be the 4-wire Toyota/Mitsubishi one of £110 each, inclusive of delivery and VAT. But on its compatability list, only Yaris from February, 2001, is listed, and the engine stated is 1NZ-FE! My 2001 Yaris has the 1SZ-FE engine. 1NZ-FE was never imported to this country I believe. Please make sure they have the right one for your engine. The contact link is at the bottom of the page. The universal unit, one that fits 'all' car makes and models, on the other hand is a real marvel: it costs only £30 each (not the one with the planar design, or at least that is what I think!). Again, it is prudent to ask first.

But wait. There is *no evidence* that the sensor(s) is the root of the problem at all. A defective oxygen sensor has its own fault code (P0420). When the mechanic said he had "done everything he could and it's still no better", there appeared not much he had done apart from flushing the fuel system. Now throwing in the towel he suggested a complete oxygen sensor replacement (viz. there was no engine malfunction, only incorrect sensor readout)! Could he not attempt testing the sensor first (with a voltmeter at its multi-plug) at the very least? Princess, change your mechanic: he is clueless, probing in the dark, and he is a shark.

The list of possible errors is long, spreading over two pages in an A4 sized book. Unless one is very lucky to hit randomly on target early, diagnosis of such a fault is a time-consuming process. The proper procedure is to follow a prescribed sequence of steps to test and evaluate various involved sensors, and operations. You need to go to a tuning specialist for that, if you don't fancy going to a Toyota dealership. There is one such in NW London. I only came to know about them through my reading. As I have no experience of the garage, I don't really want to publicise their name on here. A personal message to Princess will follow shortly.

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Bee.

Correction:

P0420 refers to cat converter malfunction.

OBD-II standardized codes:

http://www.tegger.com/hondafaq/error_codes.html

P0420 Catalyst System Efficiency Below Threshold (Bank 1)

P0430 Catalyst System Efficiency Below Threshold (Bank 2)

I got that wrong! The fault codes for oxygen senser are many in fact (see the table in the link). P0141 and P0171 are definitely two of them. Thanks to rf76 for pointing this out.

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Bee.

[rf76]

Is it a P0171 or p0141 code? If so, have a look at the air flow meter. these r common for failing n throw up a variety of codes from lean/rich mixture to oxygen sensor malfunctions. I think they're about £80+vat to replace but can be cleaned with brake cleaner.

[Bee]

....I think they're about £80+vat to replace but can be cleaned with brake cleaner.

To follow that, I might add:

“Don’t spray silicone or WD40 in the connector. Those two fluids will kill an O2 quicker than lighting. The sensor needs to breath oxygen (O2) and it does it through the wiring. Silicone will send a sensor’s output south so fast you won't know what hit you.”

"Replacing Oxygen Sensors"

http://www.allpar.com/eek/o2.html

Under "Warning", 4/5 down the page.

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Bee.

[Kal-El]

I'm about to order and replace the sensors on my Yaris. I had the dreaded P0171 code come up and was promptly reset by the local mechanic for £25. He said that he couldn't be sure with the Yaris and it could be a number of things that generate this code. Possible causes are MAF sensor. Needs a good clean and light reset. If the light comes back on then maybe the o2 sensor. Only this option costs in the region of £200!!

I'm annoyed that as a common fault with many Yari that Toyota charge through the nose for it. I am more than willing to try the universal option and will let you know how it goes...

Should have bought a mountain bike

[princess]

Is the air flow meter the MAF? Can you test these to see if they are faulty, or do you just replace and see what happens?

Does anyone have instructions for replacing with a universal O2 sensor, ie info on the wiring?

[Bee]

Is the air flow meter the MAF? Can you test these to see if they are faulty, or do you just replace and see what happens?

Does anyone have instructions for replacing with a universal O2 sensor, ie info on the wiring?

Yes, air flow meter = airflow meter (in Haynes Service and Repair Manual)

= MAF (mass air flow) sensor

= AFS (air flow sensor).

http://www.100megsfree4.com/dictionary/car-dica.htm#AIAA

It can be tested, but first, it should be cleaned to see if it makes any difference:

http://www.msnusers.com/Sorensonbrian/airf...orcleaning.msnw

Note that your Yaris has the 1SZ-FE engine, as has mine, which differs from the Echo's 1NZ-FE engine depicted in the photos in some minor ways. The air flow meter in yours is on the side of the air filter housing, secured vertically, like in the photo (5.2) on page 4A.3 of the Haynes' Manual. The cleaning procedure is the same.

The testing itself is rather involved, for apart from testing whether it is working at all (an integrity, static test), you have to test whether it is functioning properly (a dynamic test to see if it is sending the correct signals to the ECM in response to different volumes of air passing through the air filter). Using a simple digital voltmeter and a tubing (to blow hard at the sensing end bit in the 'throat' of the air intake track/trunk) is rather hit and miss. Using a digital voltmeter with max. and min. readouts is better. One with a bar gragh (histogram) costing ££ is even better. The proper setup is to use an oscilloscope while the car is running on a rolling 'road' (dynamometer), the one as used in MOT stations. The vacuum created by the running engine provides a suction force to drive the air volume in this case. So you see, testing the air flow meter to arrive at any meaningful result for a home mechanic is not that easy. Nevertheless, if you must you may try your luck doing just the static test; if it's OK, you assume the dynamic test is OK too. Or, as you say, forget the whole lot, replace the air flow meter and see what happens. For the testing procedure, if there is no further suggestion on here, you may like to look up on the web, or the local library (ask the librarian for help).

What has been said on static and dynamic tests in air flow meter testing also applies in oxygen sensor testing. It's easier as the engine only needs to idle at low and high steady RPM in a stationary car. Also, the signal output voltage switching, say in a hot engine at 2500 RPM, normally between 200 and 800 mV in a good oxygen sensor, though best observed on an oscilloscope, can be read in a simple voltmeter as a steady single readout of an average of 450 mV. Again, a proper test procedure (and interpretation of results thereof) needs to be consulted. For example, by how much is a deviation from this 450 considered abnormal? Fortunately, there are a number of well written articles on the subject on the web.

As for the wiring and pin out of the universal oxygen sensor, I think the best person to ask is the supplier. I've never replaced one myself (but I know I'll have to one day sooner or later, as it's such a common failing).

There are two more web sites in my bookmark collection showing how to replace an oxygen sensor. I have no idea whether these are of the universal variety. I should think instructions would be included with the delivered sensors. E-mail the supplier, requesting a copy of the instructions to be forwarded first (or posted on site for you to download) before you place your order.

http://forums.vwvortex.com/zerothread?id=990129

http://homepage.mac.com/vought/PhotoAlbum35.html

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Bee

[bod]

If it is of interest, about 4 hours ago I changed the O2 and Lambda sensor on a 2000 1.8VVTi with the universal 4 wire sensor from Gendan (very fast postage!). The manufacturer's instructions for the Gendan "Zirconia" sensor are available here:

http://www.fpuk.co.uk/pdfs/Lambda.pdf

Also, it seems that apart from a few exceptions Toyota's use the following wiring configuration.

http://www.lambdasensor.com/main/mcolours.htm

[Kal-El]

That diagram is really useful (universal sensor wiring against toyotas)

After reseting the light and cleaning the MAF using Bee's instructions (Thank you for the link!)

The Yari is doing just fine. If the dreaded light comes back I'll then do the o2 sensor, touching wood it has been about 2 weeks now with no light