Hi NAM Gurus....

I'm the happy new owner of a used 2003 MCS. I'm in love, but (of course) I have a puzzler.

Shortly after I got the car, I got the dreaded SES light. I've been reading the various threads with interest, and finally bought an ODB II reader. (an Actron CP9125 that was recommended in another thread).

And the Magic Code is: P2096

I found a single mention of this code in another thread: https://www.northamericanmotoring.co...5&postcount=10
But the thread was old, and I wasn't sure I could rely on it.

I found an old web page that listed the code as:
"P2096 or P2098 Post Catalyst Fuel Trim System Low Limit "

Any tips on what this might be and how I might make the light go away (other than tape over the light).

Oh... and taking it to the dealer isn't really an option (900+ miles away, no roads, welcome to Alaska!)

 

I'm no expert at Codes but what stands out is the "Post Catalyst " part. Could it be that your secondary O2 sensor is bad? Maybe someone else could elaborate. Just a thought.

 

My listing shows the following:


P2096 8342 Post Catalyst Fuel Trim System Too Lean (Bank 1)

Slightly different, but essentially the same thing - the O2 sensor after the cat is reading a too lean condition.

 

This is what I really hate about OBDII. Not enough info, just enough to get you thinking about buying parts. (why do you think AutoZone provides this service for free!)
That said, since it is a post-cat code, it kind of narrows it down to the cat or the O2 sensor (or an exhaust leak letting outside air into the system).
If you can do so, inspect the exhaust system for leaks, loose connections, etc. Could be as simple as a flange gasket gone bad.

 

Assuming for a moment that it is the O2 sensor(or an exhaust leak, for that matter), how big a deal is this? In other words, how urgent is it that I get this thing addressed?

 

Not life threatening critical, but it's not doing your car any good either. Sooner would be better.
This car is new to you, right? Do you know what, if any, mods were done to it? Is it still under warranty?

 

I don't believe that the car has any mods at all. It is under warrenty until March, but it would cost me about $1200 to get it shipped to the nearest dealer.

 

It is the engine controller's way of telling you that there is an excess of oxygen being detected by the OS sensor after the catalytic converter.

This can arise from something as simple as an exhaust system leak that is allowed outside air into the exhaust system thus adding to the oxygen content of the exhaust.

The post O2 sensor wants to see too little oxygen because this is a good sign the converter's using the oxygen present in the exhaust from teh engine to process and breakdown emissions gases in the exhaust.

One thing I've found very helpful is to have a code reader that allows me to monitor in real time (while I'm driving the car) various engine sensor values (at least the values the engine controller reports) and look for any signs of trouble.

For instance, my Porsche emitts on occasion -- though it hasn't recently -- a DTC (diagnostic trouble code) that says something to the effect the converter is failing to process exhaust gases completely.

However, when I monitor the O2 sensors on that cylinder bank, the 1st sensor being used by the engine controller to monitor and control the air/fuel mixture to the engine to keep the exhaust gases within the very narrow range the converter, and the 2nd being used to monitor the converter's performance, I find the second O2 sensor failing to react much if at all instead displaying a usually way to low volt reading that varies but is always way lower than it should be (it should run about about .7 volts) and way lower than the other bank's corresponding O2 sensor.

What is happening -- I believe -- is the O2 sensor is getting old - the engine has almost 125,000 miles and the sensors (except the #1 on that bank) are original.

The sensor doesn't do this all the time either.

So, before I replace the converter I'm going to replace that O2 sensor having already had to replace the 1st one on that side because it too exhibited the same symptoms.

In my car's case, all 4 sensors are identical and one can swap them around and see if the symptom (erratic or wrong reading) follows the sensor. If the sensor's bad, though, the diagnostic trouble code might change because the engine controller will "diagnose" a different problem.

I am not familiar with the MINI engine and its sensors (yet) but if the sensors are swappable swap them and see what happens. Obey all the rules regarding O2 sensor handling. They are very robust but delicate and sensitive at the same time.

If you can monitor the O2 sensor's voltage in real time you should see the voltage reading low and this means the exhaust gas has too much oxygen. Lean equals low voltage. And lean means a surplus of oxygen in the post catalyst exhaust flow (the oxygen content can be nearly the same as ambient atmosphere).

The 1st O2 sensor when engine hot -- and the system is running closed loop -- should swing from 0.1 volts to 0.7 volts about once per second at idle speed though older O2 sensors do not cycle as fast nor as much as new sensors.

The 2nd O2 sensor when the engine hot and running closed loop and at idle should read 0.6 volts or a little higher (I've seen 0.7 volts and a bit). High voltage means there is less oxygen in the exhaust gas stream (less than in the outside air).

Essentially the O2 sensor compares the oxygen content of the exhaust gas stream to the oxygen content of air (outside air) and as the oxygen content of the exhaust gas gets closer to the air's oxygen content generates a lower voltage signal.

As the oxygen content of the exhaust gas stream decreases and becomes less than outside air's oxygen content, the O2 sensor generates a higher voltage signal.

Sincerely,

RockC.

 

To remove the light disassemble the tach and heat the soder and lift off the LED. (sorry I couldn't resist)
It might be worth it to give MINI roadside a call, they claim that they'll get you to the nearest dealer for free, its getting it home thats on you. Definately sounds like an 02 sensor issue, but I'd put it on jacks and check for leaks first. If you reset the code does it come back? If it doesn't may just be a connection that came loose over time and bad roads.

 

My 05 MCS has had the same p2096 code. First at 8,000 miles, then probably three or four times up to 16,000. I found that changing where I bought fuel, staying always with 92 octane, the light would eventually go out. It is a fine line that kicks that SES light on. 92 Ethanol does not help at all. We have alot of that crap around here.

 

Wow, RockC.... Thanks for the detailed information. As an Automotive Newbie, I find this sort of the very interesting!

 

Thanks for responses, Ricky and "Motor On"...

I reset the code and it comes right back. I'm intrigued, Ricky, at your comment regarding bad fuel. I noticed that the light came on shortly after I fueled up for the first time. I used 91, but it wouldn't surprise me if the quality was bad.

I used 92 this time around. Maybe I'll get lucky?

If I'm not lucky, is an O2 sensor replacement a reasonable DIY project?

 

Put the car up on stands and take a look. You're looking for the O2 sensor after the big cat, right before the flange to the rest of the exhaust system. Don't know the price of the part. But while you're under there, you can check for stuff that's loose etc. I think it's connected down there with a short pig-tail, so disconecting it shouldn't be too much of a PITA.

Matt

ps, if you're in the boonies, get one of the manuals for the car. It will help big time....

 

kinda OT but I have only once seen 91 and never seen 92 and always use 93 octane, where do you buy your petrol? Also on that note next time you buy petrol use a high detergent fuel from a high turnover filling station. there was a link posted listing detergent ratings I'll see if I can find it.

 

http://www.toptiergas.com/

 

Here in CA 91 is usually tops... but there's a local 76 that sells unleaded 100 But it's almost $5 a gallon!!!!

Matt

 

The local 76 here sells 110 octane for $4.50 a gallon. I should put a 1/2 tank in someday.

 

Hmm... High detergent, eh? I'm not sure how I would know this....

I suspect that my options are limited.... for fun (and to have an excuse to drive my MINI around), I surveyed most of the Gas stations in the area. I found that their "premium" gas ranged from a low of 90, 90.5 (?!), 91, and 92. I'll look around for "brands", but I think that most of the stations are Tesoro.

 

It's a chevron product....

But if your cat or sensor are poisened, I wouldn't hold much hope for a detergent to clean it out. Those suckers run hot, and if anything will clean em, it's just by baking the crap and vaporizing it.

Cats get poisened mostly by high sulpher fuels. Don't know about O2 sensors...

Matt

 

Granted I have no idea what the code my ecu was throwing was so I don't know for sure that this is relevant to you but not too long ago I had some fun experiences with my SES light too. I filled up the tank and a few hours later the light popped on for the first time. My though was that I hadn't tightened the fuel cap well enough (this was before I realized that there is a separate idiot light for that) so I stopped and tightened it and kept going confident that eventually the light would go away. Sure enough the next day when I started the car, no light. Long story short, it came on and went off a few times over the next few weeks and almost always a few hours after filling the tank. Finally got it checked out and was told that I had a faulty post-cat O2 sensor. Got it replaced under warranty and no more light since then. This is with about 25,000 on the clock. Generally speaking the O2 sensors in our cars should go for about 80-100k before needing to be replaced but that doesn't mean it can't go bad sooner. While bad gas may have something to do with it its more likely that previous posters mentioning exhaust leaks are right, or that your O2 sensor is in fact faulty. Check for leaks, then replace the sensor if you don't find anything. With enough wd-40 and a big enough breaker bar to get the old one loose it really shouldn't be too much of a problem to swap it out.

 

Hello, I recently bought an '02 cooper with about 55K miles on it, now has about 60K and my service engine soon light appeared the other day. funny I took it to autozone for the free OBD hook-up and it gave me a code that said, code 02506 (or something like that) "emissions system - minor leak" after reading all the other threads, seems to me that the exhaust system probably has a leak. I already made sure the gas cap was tightened but no luck with that, the light stayed on. The car has also not been idoling too well lately, it actually stalled on me the other day. anyone have any idea what it might be?

 

There is a bulletin for that code, but it appears that they are unsure of the cause. Looking for intake leaks is about all you can do right now. If your scanner can give you sensor inputs, then find out what your long term fuel trims are while driving. your scanner may refer to this as bank1 long term/multiplicative, fuel trim/adaptations.

I recommend checking in with your service advisor on the status of the bulletin that contains this code. Try to get it fixed before your warranty is up, but I wouldn't make the trek for that price right now. Just clear the code and see how persistant it is.

 

Check into the price of a downstream O2 sensor, then check the price of an O2 sensor simulator. Downstream sensors seem to die much more quickly than the upstream ones, and they have nothing at all to do with how the car runs.

If you're willing to do the work, you can swap the two sensors and see if the problem "moves" to the upstream sensor. That'll confirm a bad sensor.

Rawhyde

 

The bulletin specifically states that the sensor is not thought to be the root cause.

 

Well folks, I think I may have my SES light problem fixed!

When I bought my car, I paid the $1000+ for warrenty coverage. My used Mini was still under its 3 years, but only just. Also, as I've mentioned before -- 900 miles to the dealer and no roads between.

Anyhoo... I took it in and they agreed that this issue should be covered. After conferring long distance with a Mini dealership, they decided to replace both O2 sensors. Since these appear to run over $200 a piece , I figure I'm well on my way to paying for the coverage.

Unfortunatly, it did not make the light go out. I was advised to plan a ferry+road trip in order to get it to a Mini dealership.

A few weeks later, I decided to try resetting the ECU. I followed the instructions, but it didn't seem to effect the light. However... a few days later, the light is gone! I figure, it needed to go through a few cycles before giving me the all clear.

I'm happy... I just hope it stays out. I also wonder if the ECU reset was the solution by itself, or a combination of the O2 sensors and the ECU... any guesses?