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Old 6th December 2011, 17:10   #1
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Default Santro O2 sensor issue

2 months back, while installing cng on my Santro, I had the O2 sensor tested for accuracy. This was important as the closed loop system, depended on the O2 sensor feedback to know if the air fuel ration was rich or lean.

Turns out my sensor was running only to 70% of its range.

I was curious why there wasn’t a sensor error / check engine light ON. A month back I had the car scanned (for a different reason) via Hyundai scangauge and there wasn’t any error. The CNG technician explained that in petrol mode the sensor reading is not needed to be 100% accurate but in CNG mode it has to be very accurate.



In petrol mode the car’s FE is decent, but not good. 11 to 13kmpl in Mumbai, Andheri to Bandra traffic. I mainly drive in peak hours only.

My questions are,

1. Does the sensor have to be 100% in petrol mode too? Would my FE in petrol increase if I change the O2 sensor?

2. How much does a new Santro O2 sensor cost?

3. How do I check if the replacement part is 100% working, at the service center or outside? I was thinking of fitting an AirFuel display gauge for this purpose even though I am not too much in favor of this.

I am currently running a open loop cng system due to this O2 sensor issue.

UM
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Old 6th December 2011, 20:49   #2
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Default

How was this '70% of its range' measured?
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Old 7th December 2011, 18:34   #3
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Default Re: Santro O2 sensor issue

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Originally Posted by DerAlte View Post
How was this '70% of its range' measured?
The technician connected a voltage meter to the O2 Sensor and it was fluctuating between 300 to 800 millivolts with the engine idling, while the technician said it should be between 100 and 1,000 millivolts. 2 different technicians checked it with me also watching the meter, and both confirmed that the sensor was not functioning 100%, but about 70%.


Any suggestions ?

Does the sensor have to be 100% in petrol mode too?
Would my FE in petrol increase if I change the O2 sensor?
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Old 8th December 2011, 10:46   #4
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Default Re: Santro O2 sensor issue

Hi buddy,

Exactly the same issue i am living with. My Santro perfoms superbly on the CNG mode, when it come to petrol mode the O2 sensor, it not working to its 100% accuracy. It could actually smell the unburnt fuel smell from the exhaust, where as in the CNG mode it gives high mileage.

If i run on petrol, i don't think even i am getting even 8 to 9 km/l. After running pillars to post, i still could not diagnouse the problem and the only conclusion i came with, the car run good in either of the mode i.e petrol or CNG.
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Old 8th December 2011, 12:07   #5
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Default Re: Santro O2 sensor issue

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Originally Posted by amitpunjani View Post
Hi buddy,

Exactly the same issue i am living with. My Santro perfoms superbly on the CNG mode, when it come to petrol mode the O2 sensor, it not working to its 100% accuracy. It could actually smell the unburnt fuel smell from the exhaust, where as in the CNG mode it gives high mileage.

If i run on petrol, i don't think even i am getting even 8 to 9 km/l. After running pillars to post, i still could not diagnouse the problem and the only conclusion i came with, the car run good in either of the mode i.e petrol or CNG.
Thanks for your feedback.

How much is your FE on CNG?
Mine is about 17 in traffic (no AC) and 24 on highway (with AC).
I am running a open loop due to my O2 sensor issue.

In Mumbai traffic, the petrol avg of any santro in Andheri bumper to bumper traffic (It takes 1 hr to cross 6 km) would be 10 to 11. My petrol avg on the highway is about 17 with AC. There is not unburnt petrol smell that i have noticed so far. So i disagree that the car can only run good in either of the mode i.e petrol or CNG.

my main question is that since i wish to upgrade to a closed loop cng system, should i buy a new o2 sensor and how much will that cost?
and also will it positively actually effect the petrol FE?

UM

Last edited by UniqueMods : 8th December 2011 at 12:10. Reason: grammar error.
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Old 8th December 2011, 12:17   #6
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Default Re: Santro O2 sensor issue

My FE with CNG is about 22-24 in city traffic (winters), with petrol its very low. The reason i know, because i everyday do few kms on petrol.

During summers with 100% aircon i get average about 20 km/kg, which i think its pretty decent. I do rev hard.

Infact, i have felt, the Santro behaves very well in the CNG mode rather than in petrol or may be its due to the advancer i have got installed.

I would suggest, don't waste your money on the O2 sensor,its ain't worth it.
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Old 8th December 2011, 14:17   #7
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Default Re: Santro O2 sensor issue

Quote:
Originally Posted by UniqueMods View Post
The technician connected a voltage meter to the O2 Sensor and it was fluctuating between 300 to 800 millivolts with the engine idling, while the technician said it should be between 100 and 1,000 millivolts. 2 different technicians checked it with me also watching the meter, and both confirmed that the sensor was not functioning 100%, but about 70%. ...
Amusing. 'Efficiency' is the wrong term in this context. Doesn't it occur to them that ~30% error in reading is much much better than upto 100% error that open-loop control can overlook? That is, in case the CNG system working in closed-loop thinks that the mix is not so lean, it will perhaps allow a little bit less fuel to go in compared to the ideal condition. In open-loop, even if the mix is totally lean, the CNG system will have no clue and not increase fuel. Only you will feel rough idling or a different driving feel (rough, more engine noise) as the case may be.

IMHO they should not draw such empirical conclusions, and allow the system to work in closed-loop.
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Old 8th December 2011, 14:29   #8
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Default Re: Santro O2 sensor issue

Quote:
Originally Posted by DerAlte View Post
Amusing. 'Efficiency' is the wrong term in this context. Doesn't it occur to them that ~30% error in reading is much much better than upto 100% error that open-loop control can overlook? That is, in case the CNG system working in closed-loop thinks that the mix is not so lean, it will perhaps allow a little bit less fuel to go in compared to the ideal condition. In open-loop, even if the mix is totally lean, the CNG system will have no clue and not increase fuel. Only you will feel rough idling or a different driving feel (rough, more engine noise) as the case may be.
Thanks DerAlte.

I agree that closed loop with a CNG ecu and stepper motor would be better in term of idling and running. that's why I am leaning towards a closed loop system upgrade.

Quote:
Originally Posted by DerAlte View Post
IMHO they should not draw such empirical conclusions, and allow the system to work in closed-loop.
I haven't bought the closed loop and then converted to open loop. i paid for the open loop itself, and now am going to upgrade to closed, once I am satisfied the return on investment( 2500 upgrade and O2 sensor ???) is going to make a positive difference in my running cost in both cng and petrol.

Guess I am off to Hyundai to check the price of a O2 sensor and hope and pray its working 100%.

UM
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Old 8th December 2011, 14:54   #9
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Default Re: Santro O2 sensor issue

Don't bother about the O2 sensor, it is pretty much standard, and does not suffer from the symptoms the CNG guys were pointing out. Just check with Hyundai guys first if your sensor make / model is the same as all in all other Hyundai cars, or if it is a different model. Otherwise, even they will go off on a wild goose chase.
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Old 16th April 2014, 00:11   #10
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Default Re: Santro O2 sensor issue

Anyone know what the output range should be and if fluctuations at idle would indicate a sensor problem or worse?

Also what would I be looking to shell out if diagnosed with the problem.

I'm coming off this thread so posted here as things were quite relevant as I need to know what to look for, voltage and part wise.

http://www.team-bhp.com/forum/techni...itation-3.html (Engine knocking & hesitation)
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