Catalytic Converter - Oxygen/Lambda Sensor

Sully

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?

crosstownk

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......

Frank_Leach

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/showthread.php?t=2055564963&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

Sully

Toyota Avensis '03 reg.

crosstownk

Sully wrote: »

Toyota Avensis '03 reg.

I'm not 100% sure but afaik that's a closed loop (2 sensors). Colm may know better.

Matt Simis

crosstownk wrote: »

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.

Sully

Sully wrote: »

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

Sully

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.

Sully

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.

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/allgemeineinformationen/tsb/files/EG5010_0_1_RAV42_DTC_Oxisensor_Kat.pdf

Sully

[quote=[Deleted User];60333316]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/allgemeineinformationen/tsb/files/EG5010_0_1_RAV42_DTC_Oxisensor_Kat.pdf[/QUOTE]

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.

ismynametoolong

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.

mikeystipey

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

beam99

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.

Sully

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?

beam99

If the engine light is on, yes it is possible to fail the nct, what model is your avensis? a pre 03 or post 03 { new shape } The pre 03 avensis had only 1 02 sensor called a lean burn sensor with the 4AFE AND 7AFE ENGINE. These sensors did give trouble and i have replaced many. The post 03 avensis has 2 o2 sensors this has the VVTI engine. { a black plastic cover on top of the engine saying vvti. The obd connector on the pre 03 is located behind the coin box on the right hand side of the drivere's seat and the post 03 is above the foot pedals

Sully

Its a post 03 avensis - just had a look at the engine. They were doing some testing above the footpedals when they looked. Still waiting for the call back they said they would give after we rang questioning them!

If the light is disabled and we do the NCT - I assume we will fail the NCT on emissions?

beam99

Going back to the cat u got welded in, if the cat is part of the exhaust manifold, you can not weld in a aftermarket cat. Cause for one its a time consuming job to do. Did the light just come on and you got the fault code PO420, or did it fail on emissions test.

Darragh29

crosstownk wrote: »

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......

OK, this isn't really correct. Too much oxygen means exactly that, too much oxygen. It doesn't mean the air:fuel ratio is an over rich mixture, it means the opposite, that the mixture is too lean, or not enough fuel.

OP it sounds like you don't want to spend money on the car, (using a weld in cat for a start and then looking for second hand parts). If your car was not hooked up to a diagnostic computer before the cat was replaced, to check if the lambda sensors were operating within spec, then whoever was doing this task for you didn't know what they were doing. It might be consistent with you not wanting to spend money on the car, that the outcome could have been that you brought the car to whoever was the cheapest and sometimes the cheapest price isn't the best option.

I'm not having a go at you here, but maybe put the price aside for a minute and before you go further with this, check that whoever is resolving this issue for you, has the equipment and the time to properly diagnose the problem for you.

Also, diagnostics is not just plugging the computer into the car and looking for DTC's (Diagnostic Trouble Codes). The ECU might not have an error stored but you could still have a problem that can only be identified by looking at sensor signal data, which is where really understanding the theory comes into it and also additional equipment such as emissions test equipment is necessary to sort the problem out.

Sully

Darragh29 wrote: »

OK, this isn't really correct. Too much oxygen means exactly that, too much oxygen. It doesn't mean the air:fuel ratio is an over rich mixture, it means the opposite, that the mixture is too lean, or not enough fuel.

OP it sounds like you don't want to spend money on the car, (using a weld in cat for a start and then looking for second hand parts). If your car was not hooked up to a diagnostic computer before the cat was replaced, to check if the lambda sensors were operating within spec, then whoever was doing this task for you didn't know what they were doing. It might be consistent with you not wanting to spend money on the car, that the outcome could have been that you brought the car to whoever was the cheapest and sometimes the cheapest price isn't the best option.

The price of the cat and installation was far to expensive. We were advised to consider looking at cheaper options by our main dealer. The car was tested by the computer before it was replaced (by the main dealer and another large garage) and we were advised the cat needed to be replaced. I don't recall any mention until after it was replaced and the error light came back on that the sensor was gone. It was here we decided to investigate further as they also suggested that there could by other causes for the cat to go and they wont find out until each problem is fixed one by one as such.

I'm not having a go at you here, but maybe put the price aside for a minute and before you go further with this, check that whoever is resolving this issue for you, has the equipment and the time to properly diagnose the problem for you.

Well its a large garage, with chains around the country. I would have assumed that such a company does have the equipment - bar the sensor, which they need to get from the main dealer who claim they have never even sold one. They do the welded cats a lot they said.

Also, diagnostics is not just plugging the computer into the car and looking for DTC's (Diagnostic Trouble Codes). The ECU might not have an error stored but you could still have a problem that can only be identified by looking at sensor signal data, which is where really understanding the theory comes into it and also additional equipment such as emissions test equipment is necessary to sort the problem out.

As I have said, the emissions were tested by the garage in addition to the checking the ECU. This is how they told us the sensor was gone.

A recap for those who just popped in without reading the thread in full;
EML light activated several months ago, main dealer advised cat needed to be replaced but the price was very expensive (this was checked during a service). Suggested looking for one online or a second hand one.

Asked the advise from another large garage who did a test a long time ago and claimed the CAT was gone. Called them last week as the NCT is due, they advised that they may have a cat that would fit it. Brought it in, checked it, and confirmed the cat needed replacement and advised a welded cat (€230). All done, on route home the light came back.

Next day, garage checked it using the computer and emissions test confirming the lambda sensor was gone and the main dealer could supply the part. Also commented that the cat doesn't just "go" but something causes it to go. Said sensor may be one of many causes, that they can only go buy what the computer says. They also claimed that driving around on the cat right now could damage it. Main dealer said they never even sold one of them and confirmed that the new cat could get damaged. Called garage back who said they would look into it and call us back - never got that call.

(The garriage is a very large chain with many stores around the country)

beam99

You need to see what exhaust they fitted to your car, on this model i'm nearly 100% sure that the cat is part of the exhaust manifold, and a main dealer telling you they never sold a cat or 02 sensor for this type of car is bull, parts that are sold only stay on there system for approx a month, other wise they would have a back log of parts listed on there system for years.
Ring 01 4567171 it's a toyota main dealer, give them your chassie or reg and they will tell you where the cat is located and give you a price.

Sully

The main dealer never said they never sold cats, they said they were expensive (€800+). They said they never sold lambda sensors though (€200+).

I guess ill ask them what they fitted but so far iv been told it was a "welded cat".

Darragh29

Right well you've confirmed the point I was making. The "large garage" with outlets across the country that you've referred to, does not in my opinion have the proper equipment or staff with the necessary skills to resolve this issue for you.

Sully

Darragh29 wrote: »

Right well you've confirmed the point I was making. The "large garage" with outlets across the country that you've referred to, does not in my opinion have the proper equipment or staff with the necessary skills to resolve this issue for you.

What makes you think that? They seemed to have the testing equipment anyway!

Darragh29

Darragh29 wrote: »

Right well you've confirmed the point I was making. The "large garage" with outlets across the country that you've referred to, does not in my opinion have the proper equipment or staff with the necessary skills to resolve this issue for you.

Too True :cool:

T.C.B.

Confusion!! I've an '02 Lotus Elise that has just failed its NCT because of emissions.

Results:

Low Idle

CO 9.03% (fails above 0.5%)

High Idle

Lambda 0.775 (fails if not between 0.97 and 1.03)
CO 8.31% (fails above 0.3%)


The guy at the NCT centre said it was not the catalytic converter but my mechanic reckons it is. He serviced the car last week and it's running very well since. Not a peep out of the engine management system either.

Any thoughts are greatly appreciated.

ismynametoolong

9.03 % is almost off the the scale and a car with no cats would only be in or around 1 % so I reckon your mechanic is wrong and the NCT guy is right which in itself is probably unusual. Anyway the only time i have ever seen such high readings was as a result of a contaminated or defective AFM ( Air Flow Meter ) Not sure what engine the Lotus has but it is more than likely equipped with an AFM .

T.C.B.

Thanks dude. AFAIK the engine is a Rover K-series. Just don't want to go forking out for a new cat if that's not the issue.

Sully

An update on my situation.. The exhaust started making a fairly bad rattling sound recently so driving wasn't great sound wise. Brought it into one of the exhaust fitters assuming the exhaust was broken and they said that the repair work on the catalytic converter was terrible, had came apart and needed to be repaired - they said to bring it back where we got it, who then repaired it. They also confirmed that the lambda sensor (no 2) was gone.

The main garage confirmed again they never once sold one and they took a look and found that both sensors were fitted at the front rather then one on the back and one on the front. Went back to the garage who fitted the new converter who are saying its not possible and it wasn't them but said they would speak with the mechanic on Monday about it.