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19-05-2009, 21:41   #1
Sully
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Catalytic Converter - Oxygen/Lambda Sensor

Hi folks..
So I finally got around to getting the catalytic converter replaced after two firms (one the dealer) told me it was gone after the EML light appeared. I went for the cheaper option of a welded cat as the main dealer advised going for a new one would be very expensive.

The cat was done yesterday and not long after I left the EML light came back. Brought it back today to be told that the cat doesn't just break and something causes it. Therefore, they would need to find that cause. After some testing of the emissions and reading the error on the computer - they told me that the lambda sensor has gone. They explained it regulates the emissions sent to the cat and newer modern cars have two of these. Apparently unless I get it replaced ASAP - I will damage the new cat. However, the part can only be obtained by the main dealer. They also said that there could be other problems and they wont know until this is fixed. They failed to properly explain why they never told me this in the first place or spotted the sensor was gone.

Does this make sense or am I being given the run around?
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19-05-2009, 22:01   #2
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Firstly, you were ill advised about the replacement cat. The cat simply 'catalyses' - i.e. converts gasses to make them safer. The cat is not electronic and therefore cannot report an electronic fault to the EMU/ECU/DCU triggering the EML. The sensors regulate the fuel supply by measuring oxygen levels in the exhaust gasses. Too much oxygen means unburnt fuel - an over rich mixture. There are two types - one that simply measures the lambda content before the catalytic converter and one that measures both before and after. Somebody needs to diagnose the problem correctly by reading the data returned form the/both sensor(s) along with other values. Be careful that you don't get stuck in the 'replace parts til it's cured' mentality.

You haven't mentioned the make/model/year of your motor......
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19-05-2009, 22:50   #3
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hi sully..
i can identify with emissions problems, no doubt you are going for the nct? i hae had similar problems, and like the last poster said, it is better to go to a place to get it tested properly so you will know which to replace. you hae the cat done now, apparently it was the lamda sensor, not alot you can do now except take th hit. could also be the oxigen(i think) sensor, but a proper test of the emissions will tell you..
i almost made the same mistake last week, i was put clear here what the proper thing to do..by an nct tester! about as good an authority as you can get on these things...
the mitsubishi dealerships quoted me 80 - 100 plus vat to diagnose the problem, then there's getting parts and booking the repair. there is a place in baldoyle that tests it for 65, and will fix it on the spot. i am going there in the morning, they come highly recommended

http://www.boards.ie/vbulletin/showt...5564963&page=2

here is the link to the nct guy's response, as well as the web address to the guys that will tell you exactly what you need to do. incidently, some mechanics equipment works for german cars and not japanese cars, and vice versa. there can diagnose both!
best of luck
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19-05-2009, 22:52   #4
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Toyota Avensis '03 reg.
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19-05-2009, 22:53   #5
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Quote:
Originally Posted by Sully View Post
Toyota Avensis '03 reg.
I'm not 100% sure but afaik that's a closed loop (2 sensors). Colm may know better.
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19-05-2009, 23:11   #6
Matt Simis
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Quote:
Originally Posted by crosstownk View Post
I'm not 100% sure but afaik that's a closed loop (2 sensors). Colm may know better.
Afaik, OBDII cars (after 1994ish) need one pre cat (Fueling data) and one post Cat (Emissions, measures the amount of Oxygen difference from first O2 sensor) .O2 Sensors are aka Lambda sensors. Some cars have 4 (2 sets of 2), if they have more than one Exhaust branch from the Engine Manifold (usually cars with with more Cylinders than 4).

How did they diagnose which sensor failed and which sensor is it? There are generic Universal O2s as well as spurious drop in replacements (identical fitting and cable lent to original) in addition to the main dealer part. The non-main dealer parts are much cheaper, but your mileage may vary, literally.
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20-05-2009, 06:36   #7
trevm
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Quote:
Originally Posted by Sully View Post
Hi folks..
So I finally got around to getting the catalytic converter replaced after two firms (one the dealer) told me it was gone after the EML light appeared. I went for the cheaper option of a welded cat as the main dealer advised going for a new one would be very expensive.

The cat was done yesterday and not long after I left the EML light came back. Brought it back today to be told that the cat doesn't just break and something causes it. Therefore, they would need to find that cause. After some testing of the emissions and reading the error on the computer - they told me that the lambda sensor has gone. They explained it regulates the emissions sent to the cat and newer modern cars have two of these. Apparently unless I get it replaced ASAP - I will damage the new cat. However, the part can only be obtained by the main dealer. They also said that there could be other problems and they wont know until this is fixed. They failed to properly explain why they never told me this in the first place or spotted the sensor was gone.

Does this make sense or am I being given the run around?

You would need to scope both O2 sensors and make sure both are working firstly.I've seen loads of avensis with this problem and a genuine cat is the only solution if both sensors are ok, those weld in jobs are a total waste of money
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20-05-2009, 12:42   #8
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From what I saw he put some machine on the dash which I think hooked in under the steering wheel. He had a laptop with him but I don't recall seeing him doing much with it but maybe he did. He hooked in a pipe or something under the car, I assume the exhaust, and had a touch screen ,machine monitoring results as he reved engine.

I was told the avensis only had one sensor and the weld cat was something they did everyday.

Both main dealer and this garrage, a well known one around ireland, diagnosed a failed cat when we asked them to look into the eml light on screen.
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20-05-2009, 18:31   #9
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Main dealer said they have never sold one of these sensors (in Waterford anyway). Called back the other company who wanted to call us back but they never did.
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20-05-2009, 21:03   #10
trevm
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Is yours the newer shape avensis or older shape? The newer shape has 2 o2 sensors a pre and post cat sensor.Toyota issued technical bulliton recently on catalytic convertor problems on the avensis.Aparently the coating inside breaks down causing the o2 sensor to try and over correct for an inefficient cat and hence turns the light on.
The weld in or universal cats are not big enough to catalise the exhaust emmissions and cause no end of hassle.A good genuine second hand cat if you could find one would be the best way out. New genuine cat from toyota is crazy money

http://rav4faq.kerkerinck.de/allgeme...sensor_Kat.pdf
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21-05-2009, 01:50   #11
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Quote:
Originally Posted by trevm View Post
Is yours the newer shape avensis or older shape? The newer shape has 2 o2 sensors a pre and post cat sensor.Toyota issued technical bulliton recently on catalytic convertor problems on the avensis.Aparently the coating inside breaks down causing the o2 sensor to try and over correct for an inefficient cat and hence turns the light on.
The weld in or universal cats are not big enough to catalise the exhaust emmissions and cause no end of hassle.A good genuine second hand cat if you could find one would be the best way out. New genuine cat from toyota is crazy money

http://rav4faq.kerkerinck.de/allgeme...sensor_Kat.pdf
This is the car in question;
http://szpilka1.blog4u.pl/upload/toyota-avensis.jpg

We were unsuccessful in getting a second hand cat - nobody seemed to have any and the ones online were for older versions of the Avensis. Not even a new one online. Was unaware the cat converter caused problems, we were told they fitted them daily with no problems.

That technical bulletin seems to cover another type of avensis also.
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21-05-2009, 10:36   #12
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To be honest many garages even main dealers have difficulty in diagnosing
EML / emission problems correctly particuarly where the Cat is involved. Unless the code was PO420 which is the cat effiency treshold code it is unlikely the cat is the problem. The pic you posted is a post 02 model so i am assuming it has the 2 sensor system and as the cat monitoring system is patented by Bosch diagnosis for all cars is the same. if you can post the specific code the dealer erased and the one that is now recorded I could give you/ him some pointers. The P0420 code will also only be stored after the car has completed two drive cycles ( too much detail to try and explain here ) so the chances are that if the EML came on shortly after the cat was fitted the ECM testing of the cat was not complete ie the cat is not the problem.
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21-05-2009, 11:17   #13
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my Polo had a lambda sensor problem last year and after 5 trips to Advance Tyres and some replacements the EML kept coming back on after a short while (they're not cowboys in fairness, they didn't charge me the last 3 times). They were mystified. Then got it fixed at a garage specialising in German cars and after a few months the bloody light came on again! Car's running smoothly now but light is still on. Certainly does seem to be a hard one to diagnose and put right
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21-05-2009, 18:56   #14
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Which exhaust {cat} was replaced some of the toyotas have the cat as part of the exhaust manifold, the way to know this is that the cat is located between no1 and no2 O2 sensors, you could also have a problem with the logic in the ecu, meaning the ecu is telling the engine light to come on , when there is no problem with the cat, some of them ecu's had to be replaced for that reason, I can't remember the part no of the effected ecu's, but if your model no is ZZT250, it should be located behind the glove box.
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21-05-2009, 21:30   #15
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They told me the car only had one sensor, saying modern cars (id personally have classed mine as modern!) have two. Was never given the error codes, just the problem. The light came on not to long after the weld cat was done - usually when the light is reset it takes a lot longer to come back on. From what others have said, the cat seems to be a bitch of a problem to fix.

Would a car fail the NCT over this?
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