Exhaust Emmissions Light

D

daz05

Senior member
 Écosse
Lots of topics on this one. I filled up with Tesco 99 for the first time in years as I normally use Shell V power, half way through the tank I get the emmissions light coming on but car still driving perfectly, I have noticed a reduction in mpg though about 1-2 per tank.

Anyway I filled up with BP ultimate and after 20 miles said light has gone out.

I'm assuming it's one of the lambda sensors on its way out and the light will come back at some point, any thoughts or similar experiences? I've purchased a code reader to get more detail but it hasn't arrived yet.

Is a drop in mpg common when this happens, first time in 40k? :(
 
Mine(non m) has just had the rear two sensors replaced,light still coming on :( -its had a new manifold also for light coming on,indy told me the zed runs weaker with the light on.
 
There are hundreds of reasons the emission light will come on. Many of them will cause lower mileage and/or lower power. Many other reasons will not cause any noticeable symptoms at all, except one might maybe measure higher tailpipe emissions.

If the light turned itself off, it means you went several drive cycles with no fault detected. The fact it went on could be a sign of a component starting to fail, or it could be an anomaly, only time will tell. I've had the light come on twice for different reasons, and neither problem has yet to return.

It will be useful to record the codes stored for future reference, but I think you were just unlucky and got a bad batch of fuel. Maybe Tesco's tanks were almost empty. I wouldn't worry about anything going bad just yet.
 
Even if it does go, first sensor in 40k miles is pretty good going TBH. When mine went the light never went back out again.
 
Yeah I'm just annoyed that my mpg has suffered and yet the car feels normal. Will post up the codes when the gadget arrives.
 
Mine came on the day I bought the car back in December, light was on for over a month, took it to my Indy garage and he replaced a cracked pipe, light went out for about 2 weeks and it's been in ever since, not sure of any changes as I've always had it on lol
 
Light came back on again for the second time, read the codes and got P0135 02 Sensor Heater Circuit Bank 1 Sensor 1.

My take on that is that circuit 1 is pre cat and sensor 1 is cylinders 1-3. How do I know which sensor to buy using these part numbers:

http://www.realoem.com/bmw/showparts.do?model=DU93&mospid=49424&btnr=18_0664&hg=18&fg=10&hl=3

?

Thanks
 
mine came on today .. again.

will be replaced the front 2 this time.....

nice and easy DIY daz, i usually replace these in pairs mate, so if 1 post cat goes ill replace both of them..... and vice versa, from what ive experienced the one that doesnt fail will soon follow..... they are cheap so you may as well swap the pair imo..... saves alot of messing around.

Btw if you clear the code it will buy you aittle time in terms of MOT ect ect as mine takes a few months to come back on again...
 
Cheers, I'm confused though, there are 4 lambda probes in that diagram which ones do I buy?
 
What I'm trying to say is that there are 4 part numbers from lambda probes in the manifold diagram i posted not two, just wondering which ones. I think it's part 3, but how do I know.

The post cat sensors are on a different diagram.
 
daz05 said:
What I'm trying to say is that there are 4 part numbers from lambda probes in the manifold diagram i posted not two, just wondering which ones. I think it's part 3, but how do I know.

The post cat sensors are on a different diagram.
Click to expand...


ok i see what your asking, excuse me.... their are different part numbers for each item as the second part of each sensor has a different length loom corresponding to the location....
you are correct the sensor you require is number 3 on the real oem diagram.
 
Cheers

ETA, for anyone using this thread, the real oem link I provided above is for a US spec Z4m, use this one instead.

http://www.realoem.com/bmw/showparts.do?model=DU92&mospid=49422&btnr=18_0661&hg=18&fg=10

There appears to be only one part number for the Euro pre cat sensors,

11787540167
 
My light came on had it checked out at an indy,found air leaks on intake,could have meant big trouble air leaks fixed and new sensor ( apparently the air leak took the sensor out or so I'm told)
 
mine is p0141 bank 1 sensor 2, so cylinder 1-2-3 sensor 2 with is post CAT..... from what i can see this is drivers side, ill order and replace, mines a sensor heater malfunction.
Already done one and they are really easy, so you guys take your time and DIY this.... clear the code then jobs a good un!!
 
daz05 said:
Only easy if you can get under the car, you going to write a how to?
Click to expand...

Yeah the car needs to be fairly well lifted.... I'll set the the front on ramps and jack the rear.

22mm lambda sensor remover makes life a breeze, unplug the relative cylinders 123 are closet the windscreen , 456 cylinders the closest to the front of the car....

Other than that it's home dry, un clip and remove, once done and dusted clear the codes and enjoy....

The pre cat ones are even easier as they are the same length/part code. A dealer will charge way to much for this job, you could change one in 40 mins taking it painfully slow.

When my new one arrives I'll make a DIY.
 
The TIS says you need special tools for the pre cat ones, is that not the case?

My Indy is charging an hours labour so only £40.
 
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