My check engine light came on, the error is with the front O2 sensor (heater 1 bank1 circuit low or something like this).

Where can I buy an OEM sensor for a reasonable price and what could have caused it to fail? Is this a common issue?

Thanks!

It's most likely the heater element part of the sensor that's failed as it's a very common complaint for all FI cars these days, but it's not unknown for the feed voltage to have a problem, it heats via 12v supplied by the fuse box.
(but the sensor self generates between 0.1v and 5v back to the ECU)
So a quick check at the connector with a voltmeter should see one wire report battery voltage with the key on.

The front and rear sensors are the same part, but do slightly different jobs, so can be swapped over.

The rear sensor monitors the Cats performace and does not influence fuel trim (but the front one does, that's why a duff one makes the car run like ****e), at worse all the duff heater element sensor will do is give you a Cat performance related code if fitted post Cat.

But this is doubtful as the Cats performance alters due to heat of the exhaust anyway.

There are only a couple of companies that make O2's for everyone, one is NGK (badged NTK) if you really wnat a new one.
sparkplugs.co.uk will sell you one, I've used them in our old Active and a few other cars without issue.
Not sure if it's genuine, but you could try shop4parts for one of those.

The car runs fine and the fuel consumption hasn't changed either (i would expect one or the either or both not to).

For what it's worth, the night before the Check Engine light came on I was running low on petrol and while cruising on the motorway there was a slight hesitation for a second, it happened a couple of times and I thought it may be water or dirt in the fuel.

If the sensor was the culrpit (most probably) it explains why the hesitation happened in closed loop.

Btw the front and rear sensors aren't the same: https://www.shop4parts.co.uk/?name=...)_1.4_16v_Sensor_-_Lambda&cat=Sensor_-_Lambda

In my previous car the front was a wideband, not sure if the Fiat's one is a wideband one.

You might be right, I didn't consider it being a 100hp, D'oh!
My Active both pre and post were the same part.

It's a funny issue, the heater fault.
If the heater fails, from cold start the fuel status can trips into
"Open loop - system fault" due to there being insuffient response from the O2 when it compares it to engine temp (coolant temp).
And it will continue in Open loop - system fault, running rough with unsteady idle and guzzle fuel all day.

But if you run/drive it enough so the exhaust gases heats the sensor and restart the car, it will usually go straight into "Closed Loop" and run ok as the engine temp and sensor temp are hot.

That is until it cools off again and you start all over again!

I cleared the error but it came back again soon after I started the car.

Yep, probably the fact that I do 160 miles a day (95% on motorway)means the exhaust/sensor stays nice and hot which explains why the fuel consumption hasn't changed as you say.

I've ordered a new sensor from shop4parts. Is it located on the right hand part of the engine bay (as you look at the car from the front) or is there a "how to" guide to replace it?

Where can I download the technical manual from?

Thanks again!

fpan said:

Where can I download the technical manual from?

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https://www.fiatforum.com/downloads.php?categoryid=13

You want the Panda eLearn

They can be tricky to get out and usually require a tool to remove them due to the length, the wiring, corrosion and because they are feckin tight.

I have messed about with a few different tools and find these to be rubbish and tend to slip on the nut.
Laser 2120 Oxygen Sensor Socket 22mm 3/8"d: Amazon.co.uk: Car & Motorbike

Better
http://www.ebay.co.uk/itm/like/3009...3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108

Much better
https://www.google.co.uk/shopping/p...&sa=X&ei=nCCUVPbgG4_iaKXagKgO&ved=0CEIQ8wIwCA

Can I cut the wire from the existing sensor and use a normal ring spanner?

That's what my friend did in his car (not a Fiat though).

I have always used normal open ended spanner and heat for a blow torch and normally have little issue removing it

The sensor arrived this morning (great service from shop4parts, I ordered it yesterday!).

I am planning to replace it today but can only reset the ECU on Monday as I don't have a reader with me, do you think this will be OK?

Alternatively, is there another means to clear the fault code without a reader?

Edit: I've installed eLearn but it doesn't seem to cover the 100HP.

fpan said:

The sensor arrived this morning (great service from shop4parts, I ordered it yesterday!).

I am planning to replace it today but can only reset the ECU on Monday as I don't have a reader with me, do you think this will be OK?

Alternatively, is there another means to clear the fault code without a reader?

Click to expand...

If the fault is resolved with the sensor replacement then the light should automatically extinguish after 3 clear runs

Most Easterly Pandas said:

If the fault is resolved with the sensor replacement then the light should automatically extinguish after 3 clear runs

Click to expand...

Thanks. It looks like it doesn't store historic fault codes then.

fpan said:

Thanks. It looks like it doesn't store historic fault codes then.

Click to expand...

It stores them, but it only appears as a fatal fault and brings up the MIL if its a current and not historical issue.

So I am stuck

I've removed the undertray and the heatshield bolts but I can't get the heatshield out as there is no clearance and it fouls the plastic fan cowling.

There is no clearance to rotate a spanner either as it fouls the fan cowling.

To top it all off I've cut the wire of the old sensor hoping it might be easier with a ring spanner but no.

I don't really want to remove the radiator and cowling , why do the Italians design things like this?

Or am I being stupid?

I appreciate your help guys.

fpan said:

I don't really want to remove the radiator and cowling , why do the Italians design things like this?

Click to expand...

Its far easier on the Stilo, but then again a much bigger engine bay with the same engine.

If I am lucky I may get away with just removing the cooling fan and not having to remove the radiator. I hope so.

Finally the new sensor is in and the light has switched off by itself .

It was a bit of an adventure though since removing the cooling fan didn't help so I called AA and they used a deep socket for alloys to remove the old sensor.

We nipped up the new one using a spanner.

Does anyone know the tightening torque for it?

The best tool to use is actually a crowsfoot spanner.

fpan said:

Does anyone know the tightening torque for it?

Click to expand...

Can't find anything for the Panda, but eLearn for the 1.2 500 says 45Nm.

That would fit with the recommendations on the NGK website,which suggest a figure of 35-45Nm for an M18 sensor (the 500 sensor is M18).

For the smaller M12 sensors, use 18-23Nm.

The NGK lambda sensor catalog contains much useful information. I've attached a copy to this post.

Hope this helps.