BMW 3 series warning light emission values deteriorating


hi, I back again after nearly 2 years for help.

About 2 weeks ago, the yellow light appeared ino dashborad and there was no power in car and wa vibrating. The mechanic fixed by replacing the 2 ignition coils. Now all of sudden the yellow light has appeared again which the manual indicates vehincle emission… The engine is fine and car runs fine. may be it needs to be reset so light goes away. I am driving and have an appointment tomorrow with mechanic who is BMW expert. I just need some tips or want to know if this problem is serious type i.e. lots of money. Please let me know…thanks in advance

What year 318 are we talking about? I admit I am perplexed at just what yellow light we are talking about. BMW used to have a service reminder system of lights (a couple of greens when all was good,then a couple of yellows came on when lower level issues needed attention, then some solid reds for more important issues) I not so sure what is being represented here.As to if the light means “lots of money” I would say that is a safe bet.

Sorry mate. Its a bmw 318 2002. The warning light is like engine shaped and the manual refers to as vehicle emission deterioration asking me refer to bmw dealer. The car is running fine as just two weeks ago the same light had appeared in dashboard and there was no power at all in car. This problem was fixed by AA by replacing 2 ignition coils. the warning light is back again but the car seems running fine. My worry is whether the issue is a serious one? I can’t afford to go to dealer as previouslt was ripped off. With the help of this forum I was able to to sort out the problem with gear box 2 yrs ago. The latest warning light seems according to a friend seems to be an emission fault or may be sensors he said. I am sorry iam a layman and need some guidance how do I approach. I can get diagnosed first and perhaps any suggestions will be very valuable so I can ask the mechanic to check the relevant areas.

Very sorry folks the manual refers to this problem as EXHAUST EMISSION VALUES have DETERIORATED…thanks in advance

You see how BMW mucks up simply calling a “check engine” light a check engine ligfht? this is one of the things you must get used to when working on BMW’s.“Exhaust emission values have detoriated”, who do they think they are?

In any case you will have to present us with whatever code the light represents in order for us to give you an idea of cost. At least BMW must stick to the same codes for a specified number and type failures that everyone else uses, except they have added several dozen additional codes. Hopefuly the check engine light represents one of these generic failures.

This gives me a chance to again express my feeling that a longer Federal warranty should be offered and this longer warranty should include more mandated emission equipment. Failure of mandated equipment or a mandated system should not be so expensive to repair for the car owner, at least that is how I see it.

thanks. its something to do with exhaust system. i am also told by my mate that it may be sensors. I shall get it diagnosed first and let us see… about six months ago i noticed at times when i turn left something touches below and makes rattling noise…i will never buy this car again as identifying problem seems a mission for these cars…

sangrani, the car you have is a great car (all though this greatness is dimished by the engine you have chosen, not unreliable,just not so peppy). The cars really need someone familar with them to diagnois and work on them so as to prevent the cars owner from really souring on the experience of owning a BMW. When I had my BMW’s I actually would “take the long way home” simply to drive the car longer, and I drove them 5 days a week for work. Wait till you get to drive one of BMW’s “M” cars(and drive it a bit hard), for a car person it is truly a great experience.I can still remember the first time I drove a BMW with a 6 cylinder. My first thought was “this is not my fathers’ 225 slant 6 under the hood”.

The good news is that based on what I’ve been able to glean from the thread diagnosing this problem should not be a “mission”.

The bad news is that correcting it may not be cheap.

It sounds like the downstream oxygen sensor is indicating to the ECU that the cat converter is no longer operating effectively. Diagnosis will consist of checking the signals on a scope to verify that it’s the converter and not the sensor.

The root cause may be related to the failed ignition coils. If you have a few cylinders not firing properly you can get carbon pushed into the exhaust system by those cylinders and it can coat the catalyst in the converter and render it less effective. It can coat an oxygen sensor too, but finding out which is coated is part of the diagnostic process.

Good luck at the shop.

A miilion thanks the same mountainbike. I just got diagnosed via computer and the fault is lambola sensor bank 1 which the mechanic told me… he said it’s oxygen sensor… i don’t have a clue but the mechanic seems a decent guy who is willing to help me out. He told me to come back tomorrow for repair but I shall also ask him to check the stuff as per your suggestion. The mileage of this car is 65000 only and I am surprised that parts get so easily worn out in BMW? is this normal? Please tell me if it is dangerous to drive and how much this oxygen sensor costs? any idea? Please,please let me know if you any knowledge about this fault diagnosed about sensor?..Any more valuable suggestions will be immensely useful and much appreciated… thanks in advance

You are correct to be suspicious of a oxygen sensor failure at this early mileage. If the sensor truly has failed an attempt should be made to determine if the failure was due to a contaminent present in the exaust gases, which could cause the next sensor to fail also. Many cars go 250K miles without oxygen sensor replacement. Is your man simply reading a code or has he performed any actual tests of the sensor? False 02 sensor replacement generates a lot of mail on this site.

I am troubled by the fact that you also have had ignition coils replaced, also early in the life of the car. We did see a minor amount of coil replacements actualy required so I can shrug and accept that they were truly bad.It does bother me that you write “AA” replaced the coils. Is this not out of the scope of what they fix?

Before the mechanic does anything else, have him check the PCV valve, which may have a different name on BMWs. However, if you tell him to check the PCV valve he will know what you are referring to.

On these cars, for some bizarre reason, a clogged PCV valve can lead to a code indicating a problem with the “Lambola” sensor, bank 1. If this is actually the source of the problem, it is a cheap fix.

In response to the question about whether it’s dangerous to drive, it is not. It’ll cause no safety issues or damage to other components ir systems.

I don’t know the cost, but from your posts it sounds like your guy is competant and honest. I’d trust him to do right by you. Some shops would take advantage of the opportunity to sell you a new cat converter and that’s much more than an O2 sesnor.

Hi Sangrani,

I’m aware this is a really old old post of yours re the “exhaust emissions values have deteriorated “ warning light (yellow in the shape of an engine) coming on on your BMW but I’ve just got the same warning light come on on my 2002 65,000 mile BMW Z3 and wonder what the outcome was of you getting your car looked at by the mechanic?

Was it just a sensor or was it more?

What was the final cost ( even though it was ten years ago) just to give me an idea.


When your check engine light comes on, the very first thing to do is read and interpret the code that is causing the light to illuminate. Armed with that information, you can decide whether it is something you can fix yourself, or decide what kind of shop to take it to. If you don’t necessarily trust the shop, having an idea what the problem is prior to visiting the shop is valuable.

There are literally hundreds of On-Board Diagnostic (OBD) code readers for sale costing from $15 up. Some are just an interface plug that communicates with an App that you can get for your phone. The inexpensive readers will read only the universal codes, not the BMW proprietary codes, but the Check Engine Light problem will nearly always be identified by a universal code. Readers that will read BMW proprietary codes (transmission codes, brake codes, parking sensors, etc.) start at about $150. For the owner of a 20-year-old BMW, owning at least a universal code reader is more important than a first aid kit or a spare tire.

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There is no code that comes up, it’s just the warning light illuminated thanks.

If the check engine light is illuminated, then there is a code stored in a computer that is triggering that light. What tool re you using to access the code?

I’m the driver and owner of the car, not a mechanic. So what you’re suggesting is I need to take it to a garage/mechanic who has the equipment/computer to read any error codes, yes? Thanks.

If this was my BMW I would use a dealer with the understanding that no work be done without approval . Of course there will be a diagnostic fee . I doubt if the person who started this thread 12 years ago will ever return .

Yes, that IS what he is suggesting. There is very little point to coming to this site and asking about cost to repair just because the light comes on if you have no idea WHY it comes on. There are posters that read the codes themselves with those cheap tools or they get the codes read for free at an auto parts store (in the US and Canada…) We can try to help them if they wish to fix it themselves but skill and tool limitations rise up pretty quickly.

There are literally hundreds of reasons the yellow light comes on and those codes help the diagnosis. Since you have no idea that this concept even exists, you need to take it to a shop that can diagnose the problem. BMW stands for Bring Money With for a reason… they are expensive to maintain!

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As usual, Mustangman is exactly correct. I have owned 5 BMWs and I drive them over a quarter million miles. However, my standard advice is that if you don’t want to do most of the maintenance on your own car, then owning a BMW that is out of warranty is a questionable choice…

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