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Old 22nd August 2011, 12:29   #16
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Default "Check Engine" light in Hyundai Tucson and Skoda Laura 1.8 Tsi

The Hyundai Tucson manual says that if this light comes on during driving, it indicates a problem with exhaust system (EGR related trouble, etc) and indicates that the vehicle is not meeting the exhaust regulations while the light is on.

Skoda Laura manual also says the same thing. Additionally, Skoda manual says that if this light comes on during driving, engine management software will select an engine program that will help you to drive home safely, which I can interprete as "drive slowly and cautiosly till you can find a safe stop".
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Old 22nd August 2011, 20:51   #17
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Default Re: "Check Engine" light also indicates ECU "relearning" ?

That's called 'Limp home' mode - speed limited.

The conditions you described are still 'operational errors', nothing ambiguous about that condition.
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Old 23rd August 2011, 14:08   #18
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Default Re: "Check Engine" light also indicates ECU "relearning" ?

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That's called 'Limp home' mode - speed limited.

The conditions you described are still 'operational errors', nothing ambiguous about that condition.
Right. I am thinking the same. There is no mention of ECU relearning or high altitude driving in connection with the check engine light.
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Old 8th October 2014, 19:06   #19
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Default Re: "Check Engine" light also indicates ECU "relearning" ?

The endeavour does not have an altimeter, but it has a barometric sensor that measures atmospheric pressure. The mechanics at service center misqoute it as oxygen sensor.

Now at a particular atmospheric pressure as programmed in the ECU which corresponds to about 16000 ft. the engine cheque light comes on continuously.

I recently returned from an extensive tour of Ladakh and noticed that at about 16000ft, some times less sometimes more the light comes on, but I did not notice drastic change in the performance of the vehicle. In any case at that height one goes slowly as such. But the manual is grossly inadequate in explaining it.

In my case the light refused to go off on comming down untill the engine was switched off for 30 mins or so after which on restarting it would not come on. I dont know if this is normal, logically it should go off on its own on comming down.

While returning the light came on twice at a much lower height even after cancelling the error code of low barometric pressure at a service center at Ludhiana. So I opend the sensors and blew air with the blower for cleanin my camera lenses. it lighted up again even on reaching noida but the next morning it was gone and has been ok for one week now. So probably the dusty atmosphere of Ladakh played some role. Because these sensors are interpretated by the amount of current passing through them to the ECU. So a slight drop in current or voltage will be mis-interpretted by the ECU.
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Old 8th October 2014, 21:09   #20
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Originally Posted by MNandy View Post



Now at a particular atmospheric pressure as programmed in the ECU which corresponds to about 16000 ft. the engine cheque light comes on continuously.



.

Maybe its preprogrammed, but I don't think so. For one thing there isn't an absolute barometric pressure that is equal to 16.000 feet. Barometric pressure varies all the time, due to weather and such. Obviously, at higher altitudes the pressure becomes less, but you will still see the same fluctuations. So I cant think of how you program an altitude based on barometric pressure into the ECU. Cant see the reason for having such a setting preprogrammed either?

Here is what I think happens. As you drive in the mountains where you gain or lose relatively a lot of altitude in a short space or time and or distance, the long and short term fuel trim get out of whack. Your long term fuel trim is in essence a sort of a reference or baseline how much fuel to inject into your engine. The short term fuel trim makes small adjustments on the long term trim. When you drive up a mountain, pressure decreases sharply, air becomes thinner, your engine gets less air, starts running rich and the short term fuel trim starts adjusting. However, at this point the long term fuel trim is really not accurate enough as a reference, because it was based on much dense air (lower altitude). The ECU will keep adjusting both and when both are correct the Engine Check Light will disappear. And will reappear once the two are out of step again.

I don't think its of any major concern, but I would like to see what codes the ECU throws.

Jeroen
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Old 12th October 2014, 22:53   #21
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Default Re: "Check Engine" light also indicates ECU "relearning" ?

Hi Jeroen, While the error codes were being deleted at the service center I noticed that it was mentioning 'low barometric pressure....'. Hence, my interpretation is that the ECU operates in response to a barometer. In fact I noticed that the light would come up at some height at about 16000 ft (Sometimes more some times less which is perfectly understandable). I did not notice any restriction of RPM to low levels either. My only concern was that the light was not going off on its own on coming to lower height. Only on switching off the engine for about 30 mins and on restarting the light would remain off till again I went above 16000 odd ft. I would assume that it should go off on its own logically for me to understand that it is a normal thing happening. Unless it goes off on its own, the suspicion that something really is wrong creeps up in mind. I fact in Delhi this has happened to me earlier and it was due to excess carbon in the EGR valve and exhaust manifold which had to be cleaned. In fact I read at some internet sites in the US about ford trucks that this should be cleaned every 50000 kms...In India ford fellows don't say anything about this. Also the US sites say that the weakest thing in ford trucks is the sensor that checks the nitrous oxide levels and regulates EGR (DPCC sensor I guess)...most of the time this goes kaput and results in the engine check light coming on.
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Old 13th October 2014, 08:37   #22
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Default Re: "Check Engine" light also indicates ECU "relearning" ?

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Originally Posted by MNandy View Post
Hi Jeroen, While the error codes were being deleted at the service center I noticed that it was mentioning 'low barometric pressure....'. Hence, my interpretation is that the ECU operates in response to a barometer. In fact I noticed that the light would come up at some height at about 16000 ft (Sometimes more some times less which is perfectly understandable). I did not notice any restriction of RPM to low levels either. My only concern was that the light was not going off on its own on coming to lower height. Only on switching off the engine for about 30 mins and on restarting the light would remain off till again I went above 16000 odd ft. I would assume that it should go off on its own logically for me to understand that it is a normal thing happening. Unless it goes off on its own, the suspicion that something really is wrong creeps up in mind. I fact in Delhi this has happened to me earlier and it was due to excess carbon in the EGR valve and exhaust manifold which had to be cleaned. In fact I read at some internet sites in the US about ford trucks that this should be cleaned every 50000 kms...In India ford fellows don't say anything about this. Also the US sites say that the weakest thing in ford trucks is the sensor that checks the nitrous oxide levels and regulates EGR (DPCC sensor I guess)...most of the time this goes kaput and results in the engine check light coming on.
There is a barometric pressure sensor, it's just not possible to correlate barometric pressure to a given altitude. Depending on circumstance that will vary.

In general, as long as you don't get any noticeable performance degradation or the engine going into limp home mode or such there shouldn't be anything seriously wrong. There are dozens if not hundreds of thing that can go wrong on a modern engine which would get the CEL on. What is usually means is that the emission is (potentially) sub optimal. Unless you are very concerned about the environment, it's usually not a big thing. For instance a fuel cap not fitting tightly might cause the CEL to come on.

NOt sure why in your case it won't disappear by itself whilst driving, but as it does disappear after you shut down, again an indication that it is nothing serious. The only way to figure out is to read the error codes when you see the CEL and look up what they mean exactly.

My bet is still on something akin to what I described earlier. The high altitude throw the engine tuning a bit, thus you get the CEL. I seem to recollect that some engine management systems have high altitude performance settings. Such a mode would be triggered by Low pressure signal from the respective sensor. Again, the actual altitude isnt relevant, the barometric presure is.

Jeroen

Last edited by Jeroen : 13th October 2014 at 08:38.
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Old 22nd August 2016, 19:42   #23
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Default Re: "Check Engine" light also indicates ECU "relearning" ?

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Originally Posted by Jeroen View Post
There is a barometric pressure sensor, it's just not possible to correlate barometric pressure to a given altitude. Depending on circumstance that will vary.

In general, as long as you don't get any noticeable performance degradation or the engine going into limp home mode or such there shouldn't be anything seriously wrong. There are dozens if not hundreds of thing that can go wrong on a modern engine which would get the CEL on. What is usually means is that the emission is (potentially) sub optimal. Unless you are very concerned about the environment, it's usually not a big thing. For instance a fuel cap not fitting tightly might cause the CEL to come on.

NOt sure why in your case it won't disappear by itself whilst driving, but as it does disappear after you shut down, again an indication that it is nothing serious. The only way to figure out is to read the error codes when you see the CEL and look up what they mean exactly.

My bet is still on something akin to what I described earlier. The high altitude throw the engine tuning a bit, thus you get the CEL. I seem to recollect that some engine management systems have high altitude performance settings. Such a mode would be triggered by Low pressure signal from the respective sensor. Again, the actual altitude isnt relevant, the barometric presure is.

Jeroen
Dear Jeroen,
I am replying to this after a long time. Reason being all this time I was not able to figure out why the problem was not getting solved inspite of repeated visit to the service centre. As it happened the CEL was coming up in the plains too frequently an I noticed that whenever I would drive past 100 kmph for some time at a stretch the light would come up and then if I stop for some time and then restart and drive it would remain lighted. Now when I stop for a second time then restart it would go. The service centres changed the EGR valve without any effect (They were good enough to take back the new part after a few days though and gave back my original one and refund me the money) then they replaced the MAF sensor without any effect. Finally I started reading in the net about the codes and meanings and how to read the different parameters that they check with the computer attatched to vehicle viz. fuel trims long term and short term and how to interpret the findings and the graphs including how the ECU works to maintain the fixed stoicheometric ratio of air:fuel mixture etc. etc. and explained to the foreman whatever I learnt and then only he found out that in the beginning in 2014 when they had cleaned the exhaust manifold etc they would have detached the hose to the turbo and during refitting they did not do it properly and there was leakage. Now that being a high pressure system the problem was coming up at higher speeds. After this I have not had this problem in the past 3 months. This whole experience has lead me to conclude that the ford engineers are not taking training classes of their mechanics. And me being a doctor have to study these things for weeks together to give them an idea as to how they should logically take on the problem step by step!!!!
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Old 22nd August 2016, 22:13   #24
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Default "Check Engine" light also indicates ECU "relearning" ?

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Originally Posted by MNandy View Post
Dear Jeroen,

I am replying to this after a long time. Reason being all this time I was not able to figure out why the problem was not getting solved inspite of repeated visit to the service centre. As it happened the CEL was coming up in the plains too frequently an I noticed that whenever I would drive past 100 kmph for some time at a stretch the light would come up and then if I stop for some time and then restart and drive it would remain lighted. Now when I stop for a second time then restart it would go.

And me being a doctor have to study these things for weeks together to give them an idea as to how they should logically take on the problem step by step!!!!

Thanks for reporting back on this one and glad to see it sorted at long last. It just proves what I have been saying in many threads on the forum.

When a modern car develops a problem, get error codes read with a car specific OBD analyser and a competent mechanic who knows what he/she is doing. As a starter they should follow the formal trouble shoot guide per code as per the workshop manual.

Not sure how your initial symptoms on this problem (seemed related to high altitude) but I guess it could be.

When multiple codes pop up it still makes sense to run through the various checks first.

Most likely somewhere it would have said: check for leaks. A very simple but pretty effective way to look for leaks and or poor electrical connection is to start the engine, let it idle and start pulling, poking and hitting all inlet pieces of pipes and all electrical connections. If you touch something and the idle rpm changes you might be onto something!

Most so called electronic problems these days are not electronic at all. 99% of the time it's something more mechanical (as in your case) or simple electrical problems (e.g. A poor switch/sensor, a poor electrical connection, an air leak etc)

Whereas these are very simple things to fix they can be a real bugger to trouble shoot. It does take a good analytical mind, so I'm sure Doctors such as you can figure it out if and when you put your mind to it. But of course a proper car mechanic should be able to do so as well. In all honesty I don't think Indian mechanics are unique. In the western world there are many car mechanics who haven't got a clue. But probably there are a fair number that do. The big problem in Europe it is hugely expensive to have a proper mechanic trouble shoot this sort of stuff.

I like to do my own trouble shooting, partly for the money but mostly because I enjoy it. I have invested in a very advanced OBD analyser for my Jaguar, called Auto enginuity, including the Jaguar enhancement pack cost USD 500. As the Jagaur dealer in the USA used to charge around USD 175 just for reading the error code, it was an easy business case to make to my wife. ( Can you imagine dear how much money I will be savings us? )

My Jaguar has developed some electrical gremlins. So here I spend last weekend reading codes and cleaning endless ground connections (several dozen), pulling every fuse ( more then a hundred), pulling every relais ( about 50 or so) and taking every connector apart ( lost count). But, touch wood, it seems to have worked so far!

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Jeroen

Last edited by Jeroen : 22nd August 2016 at 22:20.
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