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Hi Guys, wondered if anyone could shed some light on this issue i have.

I have recently purchased an MX-5 2005 limited edition (only 2months ago from a garage in Sydney) and have been thrilled to bits with it , however the last 2days a warning light has come on the dashboard, (the yellow engine one that says to contact Mazda ) so i took it for its 50,000km service today and asked them to look at the warning light fault.

On picking the car up from the garage, they informed me that the fault was due to a faulty front oxygen sensor and that to replace would cost $468.80!!!! and $100 on top for fitting..!!!!

The guy at Mazda said that the car will still run properly, but i could have poor fuel economy!

Is this all the sesor is doing??? And will it have any other issues for me later on down the track?
How long do these sensors last???
Is there an aftermarket one for the NC model???

As you can see i am a little puzzled as to why something like this cost $468.80!!!!

Appreciate any advice guys,

I understand from your post that the oxygen sensor problem is the opinion of a Mazda dealer. How many km has the car done? Mazda parts prices can be at times. Is it worth getting a second opinion? Check all the wiring plugs you can see near the engine are securely connected.

$468 includes the cost of the lube for when they bend you over.

Go to Repco, buy a generic sensor for <$100 and a 22mm(?) spanner, go to Jaycar and buy a crimping tool for $30. (guess)

Hi mate, yes that's what they have told me today. The car has only done 50,000kms, surely it should last more than this!!!
A second opinion wouldn't be a bad idea. Would a normal garage be able to tell this though or would i have to take it to another Mazda dealership?
I will also check the wiring and plugs myself.
Appreciate your help mate.

JBT wrote:I understand from your post that the oxygen sensor problem is the opinion of a Mazda dealer. How many km has the car done? Mazda parts prices can be at times. Is it worth getting a second opinion? Check all the wiring plugs you can see near the engine are securely connected.

LOL... You probably not wrong there matty!!! The robbin shifty buggers!!! I even asked the guy if he has made a mistake and should it have been $4.68.... He said NO though!!! @@@T..

However can you explain to me or point me as to where i can do the "generic sensor" thing myself mate? Sorry but i haven't got much of a mechanical mind.... I just drive it with a bloody big smile on my face

Matty wrote:$468 includes the cost of the lube for when they bend you over.

Go to Repco, buy a generic sensor for <$100 and a 22mm(?) spanner, go to Jaycar and buy a crimping tool for $30. (guess)

From what I can discern the Oxygen Sensor should not be failing for such a new car?
Maybe it was dodgy from factory...
I've only heard of NB generation oxy sensors failing of late with many more years under the belt...

What Matty means is that usually they're made by one company for a few different makes of car eg. Bosch
hence a certain... genericness
Talk to a guy over the counter at an auto parts store, they should be able help
"I need an oxygen sensor for a '05 MX5" or something along those lines should be enough

Cheers and i agree it does seem a little strange as to why its only lasted 50,000kms as the car has been well looked after from what i have seen and been told, what i was asking matty for was if there had been a detailed description somewhere on here on "how to install the oxygen sensor" mate. I have no idea as to where they go!
I will check out the auto parts stores and see what they say though.

PUR157 wrote:From what I can discern the Oxygen Sensor should not be failing for such a new car?
Maybe it was dodgy from factory...
I've only heard of NB generation oxy sensors failing of late with many more years under the belt...

What Matty means is that usually they're made by one company for a few different makes of car eg. Bosch
hence a certain... genericness
Talk to a guy over the counter at an auto parts store, they should be able help
"I need an oxygen sensor for a '05 MX5" or something along those lines should be enough

The oxy sensor(s) fit in the exhaust pipe - click here for description.

I haven't looked to see where they are in the NC. Sounds a bit dodgy that one would fail at such low km - my NA8 did over 140,000km on it's original sensor and it was still working fine.

You could try for an opinion from some other place but the Mazda dealers may be the only ones that can decode the engine fault code.

My first oxygen sensor failed at around the 50,000km mark and Mazda replaced it under warranty. Last time it was checked the replacement was still working fine with 100,000km on it.

Awesome, many many thanks JBT, appreciate your help mate.

All the best.

JBT wrote:The oxy sensor(s) fit in the exhaust pipe - click here for description.

I haven't looked to see where they are in the NC. Sounds a bit dodgy that one would fail at such low km - my NA8 did over 140,000km on it's original sensor and it was still working fine.

You could try for an opinion from some other place but the Mazda dealers may be the only ones that can decode the engine fault code.

Hi Garry,

I might just give MAzda a quick call to see what they say as i totally agree you would think a part that costs so much would last longer than 50,000km!!!

Appreciate your help mate.

Garry wrote:My first oxygen sensor failed at around the 50,000km mark and Mazda replaced it under warranty. Last time it was checked the replacement was still working fine with 100,000km on it.

O2 sensors can be pretty sensitive and some junk in the petrol may have set it off. Do you know if they cleared the code when they scanned it? If not just disconnect the battery for a few minutes and it will be cleared. You may find it wont come on again. Did you change fuels or put any additives in?

The NC has 2 sensors and as everyone has said it is pretty rare for one to fail with those k's. Again as suggested check the plug and wiring - they can touch the manifold and burn through the wiring and short out.

As for the price... be thankful its the "cheap" front one... the rear one is over $600!!

Hey Mx5racing, its funny you should say that as the same warning light came on about a month ago and when i took it to the same garage, they informed me that it was a "rich fuel mixture" and they then reset it. At the time i had only been putting normal unleaded 95ron petrol in, but after this little episode, i decided on just using 98ron from now on. Apart from this nothing else. (no additives)
This time they didnt clear the code (when the diagnosed the O2 sensor). And this time it has just had its 50,000km service. Should they have cleared the code??

Thank crunchie its not the back one then indeed!!!!

Thanks for the info mate, very informative and greatly appreciated....

Cheers

mx5racing wrote:O2 sensors can be pretty sensitive and some junk in the petrol may have set it off. Do you know if they cleared the code when they scanned it? If not just disconnect the battery for a few minutes and it will be cleared. You may find it wont come on again. Did you change fuels or put any additives in?

The NC has 2 sensors and as everyone has said it is pretty rare for one to fail with those k's. Again as suggested check the plug and wiring - they can touch the manifold and burn through the wiring and short out.

As for the price... be thankful its the "cheap" front one... the rear one is over $600!!

snowboardingmr.p wrote:However can you explain to me or point me as to where i can do the "generic sensor" thing myself mate? Sorry but i haven't got much of a mechanical mind.... I just drive it with a bloody big smile on my face

Pretty much all narrow band O2 sensors work in the same way. There are two major variations between them: The thread size where they screw into the exhaust, and the plug shape where they plug into the wiring loom.

For the first issue, you need one of the correct thread size.

For the latter issue, that's why Mazda is trying to screw you over. But you can buy generic sensors that have no plug attached, just bare wires. You cut the plug off your old sensor and crimp it on to the wires of the new sensor.

I'd be inclined to disconnect the battery to clear the code and then see how long it takes to come back on. There is always the chance there is/was a bit of crap in you fuel and this has sent a wrong signal to the ecu which has stored the code only to then reset itself. Usually with faulty O2 sensors it runs a little rough at idle and uses more fuel (sometimes smells a rich at the exhaust). Still check the basics and with all due respect to the Mazda dealer, make sure the technician knows what he's doing with the scan tool. Bad wiring, etc will give the same fault code as a dud sensor. One costs $500 +, the other 10 minutes of your time.....