Seat Leon oxygen rich sensor

[LtLunchbox]

Hi,
About a month ago the engine management light came on my Seat Leon 2013 1.4 (non act) FR, I took it to the garage, they plugged it in, and saw that the lambda/oxygen sensor was reading too rich. The timestamp was when I had <20 miles of fuel left in the tank, so I thought it might have been something to do with that and chalked it off. They cleared the code and said to come back if it came up again.

Predictably it came back 2 weeks later, I took it back to the garage, was the same issue, so they replaced the sensor completely (£280 parts and labour, I thought this was a bit high?) and said that that should fix it.

That was on Wednesday, on Friday as I was driving home, the light came on again. I ordered a basic OBD reader, and it's the same issue - P2196 oxygen too rich, and on the same sensor they replaced.

I'm going back in on Monday so they can have another look, just wanted to check:

- If anyone else has had an issue like this (On a seat or any other VAG car)?

- If anyone has any idea what else it could be? (I've seen links to vacuum lines and turbo actuators that I don't want to think about £££)

- If this seems normal for diagnosis of an issue and how it's being sorted? This is my first car I've owned, and I've just moved to a new city, so I just chose the highest rated VAG specialist to go to, but I'm not sure if I'm being mucked about

Thanks for reading, and if anyone has anything to add it would be super helpful

[stevieturbo]

If the sensor is reading rich ( ignore generic OBD codes as often they are misleading and meaningless...but dont try and tell hucker that )

Then you need to find out why it is reading rich and if it functions at all ( and also check mixtures to see if it is actually rich and if so, exactly what they are ). Throwing sensors at it is a little pointless

[LtLunchbox]

Thanks for replying, I'm assuming that the sensor is working properly, as it was a new one put in on Wednesday (Bank 1 Sensor 1). This is the same sensor that's throwing up the error on OBD, so it definitely seems like it's something else.

I would also assume that the garage would check any other causes it could be (MAF sensor, vacuum line etc) before deciding to replace the sensor. Before they replaced it they told me that the old one was giving garbage data/was unreadable so I thought that they identified the sensor as the problem.

Also like I said, this is my first owned car and a new garage I haven't used before, so I'm not sure if this is normal service/diagnosis procedures

[Smiljan]

Not had this fault myself but this article does a decent job of explaining why it sets and what should be done to find out what is wrong.

https://www.yourmechanic.com/article/p2196-obd-ii-...

[Smiljan]

The additional notes make interesting reading too

Article said:

Additional comments for consideration regarding the P2196 code
It is a common mistake to assume a rich condition is a result of too much fuel being injected into the motor. The more accurate reasoning is there is too much fuel in relation to air. Hence, the term air fuel ratio. Whenever diagnosing a code such as this, it is paramount to always consider this. It is very common to have a bad ignition component, or lack of spark to a cylinder, yet the PCM will still command fuel to the injector. This will result in unburned fuel being pumped into the exhaust. Now the relation between oxygen and fuel has changed in the exhaust system and the O2 interprets this as less oxygen which the PCM interprets as more fuel. If the O2 sensor sees more oxygen in the exhaust, the PCM will interpret this as not enough fuel or a lean fuel condition

Does the car have good service history, can't harm to take a look at the spark plugs.

[LtLunchbox]

@Smiljan
Thanks for the link, I'd had a look at that article but skimmed over that part. In terms of service history, it had MOT in Oct, with the lambda sensor passing, then I had a minor service done just after I bought it (Mid Nov), and there was nothing to report then. Just had a look through the documents/services reports I got with the car, and can't see anything nasty in there either.

Also, the car doesn't actually feel any different to drive since this light came on. It felt a bit 'lighter' and more responsive after the sensor was changed on Wednesday, but that could have been placebo.
I would assume a spark plug/ignition issue would be more obvious in terms of performance/sounds?

[stevieturbo]

LtLunchbox said:

Thanks for replying, I'm assuming that the sensor is working properly, as it was a new one put in on Wednesday (Bank 1 Sensor 1). This is the same sensor that's throwing up the error on OBD, so it definitely seems like it's something else.

I would also assume that the garage would check any other causes it could be (MAF sensor, vacuum line etc) before deciding to replace the sensor. Before they replaced it they told me that the old one was giving garbage data/was unreadable so I thought that they identified the sensor as the problem.

Also like I said, this is my first owned car and a new garage I haven't used before, so I'm not sure if this is normal service/diagnosis procedures

Assume nothing..Assumptions are the ......

And often generic replacement sensors can be crap, and confuse matters more. Not always, but seen it plenty of times. However they are much cheaper than OEM sensors, so something to consider.

But again, you need to be testing and viewing data from the sensor, and actually checking mixtures to see what is happening. Not what you assume should be happening. And assuming all garages will check these things...sadly many garages are incompetent at diagnosing faults, or even having equipment to do proper checks.

Problems are not always easy to fix at all, but some do make them harder than they need to be. But when so may problems could give the perception of a rich condition at the sensor....lots of things do need checked.

[Tony1963]

How many miles has the car done? When were the plugs last changed? At least check them.

[keithb8]

Hi, I know this is an old post but did you find a long term solution?, I have the same issue with a 2014 leon 140hp fr both sensors appear to be operating & the long term fuel trim is -0.78% (OK) with fuel consumption as normal. I've read elsewhere that the downstream o2 sensor can cause this issue, mine is reading 0.75v at idle but dropping to 0.1v at higher revs.