[anandpadhye]

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".

[DerAlte]

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

The conditions you described are still 'operational errors', nothing ambiguous about that condition.

[anandpadhye]

Originally Posted by DerAlte

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.

[MNandy]

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.

[Jeroen]

Originally Posted by MNandy

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

[MNandy]

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.

[Jeroen]

Originally Posted by MNandy

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

[MNandy]

Originally Posted by Jeroen

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!!!!

[Jeroen]

Originally Posted by MNandy

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!



Jeroen

[su1978]

Last week while driving down the NH2, now called NH-19, from Patna to Delhi, late in the afternoon, i would be going around 110-120 on my honda mobilio Idtec. The car has just done 37000 kms till date and has been serviced at only Honda service stations as per the prescribed schedule. Suddenly, the Check engine light blinked and the ECO mode got turned off. Car felt a sudden loss of power for half a second and regained speed. Then this phenomena continued for around 15-20 times. I slowed down the speed to around 80-90 and then this problem never appeared during the entire journey. Luckily, i had the OBD-II fitted in my car and i tried diagnosing the problem. No error codes were shown.

Can someone please guide me if this could be due to adulterated fuel(please note that i tanked up only at Reliance fuel outlets) or due to continuous high speed that i had maintained since morning. Or is this due to some other issue. I will definitely take my car to the Honda people but still any first hand information here would be helpful. Please guide.

[Jeroen]

Originally Posted by su1978

Suddenly, the Check engine light blinked and the ECO mode got turned off. Car felt a sudden loss of power for half a second and regained speed. Then this phenomena continued for around 15-20 times. Luckily, i had the OBD-II fitted in my car and i tried diagnosing the problem. No error codes were shown.

Can someone please guide me if this could be due to adulterated fuel(please note that i tanked up only at Reliance fuel outlets) or due to continuous high speed that i had maintained since morning. Or is this due to some other issue. I will definitely take my car to the Honda people but still any first hand information here would be helpful. Please guide.

I would think if you have adulterated fuel, or rather fuel that is way of spec, the problem would persist. It certainly should not be due to continuous high speed driving. That is normal operations as far as a car is concerned.

The fact that your OBD did not show anything doesn’t necessarily mean anything as it is unlikely to read your car/engine specific codes, only the generic error codes. So best get it checked and read with a car/engine specific reader. Let’s take it from there.

It could be all sorts of things, but obviously nothing serious as your car is still running fine. Sometimes this happens and you might never find out why, but always best to check and make the effort to see what was wrong.

Good luck

Jeroen

[su1978]

Originally Posted by Jeroen

I would think if you have adulterated fuel, or rather fuel that is way of spec, the problem would persist. It certainly should not be due to continuous high speed driving. That is normal operations as far as a car is concerned.

The fact that your OBD did not show anything doesn’t necessarily mean anything as it is unlikely to read your car/engine specific codes, only the generic error codes. So best get it checked and read with a car/engine specific reader. Let’s take it from there.

It could be all sorts of things, but obviously nothing serious as your car is still running fine. Sometimes this happens and you might never find out why, but always best to check and make the effort to see what was wrong.

Good luck

Jeroen

Yes sir...i will definitely take my car to Honda to get the exact reason for this issue. The reason why i suspected it out of adulterated fuel is because, i tanked up in Bihar and that too on a highway where i did not find many vehicles. Many of us are aware that anything is possible in bihar. Please help clear my understanding if this could be even due to something clogging the injectors periodically and since i was driving very fast hence the pressure on fuel rail very high and it passed off and now that the fuel lines/injectors are clean, the car is running fine and all right. Also please note that i was again driving fast post midnight at around 110-120 and this problem did not re-occur.

Yes you are true in saying that the OBD that i use to communicate with the car has some very generic fault throwing capability and was not able to tell me the correct code

[Jeroen]

Originally Posted by su1978

. Please help clear my understanding if this could be even due to something clogging the injectors periodically and since i was driving very fast hence the pressure on fuel rail very high and it passed off and now that the fuel lines/injectors are clean, the car is running fine and all right. Also please note that i was again driving fast post midnight at around 110-120 and this problem did not re-occur.

I would expect the filter to clog, not the injectors. If they do, you have a major problem and probably some major damages. Driving fast or slow typically doesn’t alter the pressure on the fuel rail.

As your car appears to running fine now I wouldn’t worry. It could have been all sorts of things. The problem of these one-offs is trouble shooting. There might be nothing that you can find.

Good luck, let us know what happens.

Jeroen

[lurker]

I have a Check Engine Light since past 3 years in my dzire petrol. OBD at service centre revealed it is related to EGR. Now this hasn't hampered performance till now and car is running normally. MASS asks me to replace EGR for ₹10k. This car has run around 25k.

Should I clean EGR or change it altogether. This light started coming on only after a routine service on the car sometime in 2015.

Another thing is this light disappears for a while after long highway drives or sometimes when pressure washing underbody.