Engine Warning Light

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Gooseacre
Joined: Thu 10 May, 2012 19:18
Posts: 152

  M roadster S50

Engine Warning Light

Post by Gooseacre » Mon 04 Apr, 2016 14:20

Hi all,

Just thought I'd post and see if there are any pearls of wisdom out there. The yellow engine warning light has just come on on my S54 (104k miles). Have had a few issues on and off since I had that with no discernible pattern it is underpowered - grumbly under any kind of acceleration. Completely comes and goes - eg. out in the morning and grumbly and then on the return back to normal. If anything, with the light coming on, engine seems smoother than ever.

Obviously going to take it to my local indy (CPC) for a fault check. His guess was lambda sensor.

Only other thing was this morning there seemed a lot more coming out of the exhaust but could have just been the coldish weather.

Sometime when I park up after even a short run exhaust gases still seem to leak out of the exhaust - and often only one side. Always strck me as a little odd.

Any thoughts out there?

David
2001 Z3M S54 LB64010 #10/73
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Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2121

  Z3 roadster 1.9

Re: Engine Warning Light

Post by Del » Mon 04 Apr, 2016 16:42

The intermittency does suggest a sensor gradually failing – a full diagnostics should pinpoint it.

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pingu
Joined: Fri 30 Apr, 2004 17:01
Posts: 3337

  M roadster S50

Re: Engine Warning Light

Post by pingu » Mon 04 Apr, 2016 17:45

Del wrote:The intermittency does suggest a sensor gradually failing – a full diagnostics should pinpoint it.
Yes, the diagnostics check will show the history of the fault as well as it's current status.

Your mechanic may need specific BMW software, such as INPA, to show history.
Pingu

Gooseacre
Joined: Thu 10 May, 2012 19:18
Posts: 152

  M roadster S50

Re: Engine Warning Light

Post by Gooseacre » Thu 21 Apr, 2016 10:06

Turns out no fault on lambda sensors

Fault was something like "inefficient catalytic conversion". Warning light reset and not come back on again.... yet

I though cats should last beyond the 104k my S54 has on it?
2001 Z3M S54 LB64010 #10/73
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Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2121

  Z3 roadster 1.9

Re: Engine Warning Light

Post by Del » Thu 21 Apr, 2016 10:27

It sounds as if your post cat lambda(s) have triggered the “error light” as their main purpose is to measure cat efficiency. Assuming the sensors are not faulty, it means the fault lies with the cat itself. There are cleaners that can be put into the petrol to clean the cat that MAY help – I’ve heard good reports about Cataclean and the Forte products. Some people are not keen on "additives" – you might want to take advice from your mechanic before sticking stuff in your valuable car.

Gooseacre
Joined: Thu 10 May, 2012 19:18
Posts: 152

  M roadster S50

Re: Engine Warning Light

Post by Gooseacre » Thu 21 Apr, 2016 10:35

Thanks - will consider

Its odd that the inefficient conversion has shown up now as it was MOTed just a couple of weeks previously and therefore passed the emissions test. Guess the tolerance on the lambda sensor is less than the tolerance in the MOT rules!
2001 Z3M S54 LB64010 #10/73
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pingu
Joined: Fri 30 Apr, 2004 17:01
Posts: 3337

  M roadster S50

Re: Engine Warning Light

Post by pingu » Thu 21 Apr, 2016 11:31

Gooseacre wrote:Thanks - will consider

Its odd that the inefficient conversion has shown up now as it was MOTed just a couple of weeks previously and therefore passed the emissions test. Guess the tolerance on the lambda sensor is less than the tolerance in the MOT rules!
The sensors are pre-cat, the MOT emissions are measured post-cat.

As a guess...If you have a leaking exhaust (pre-cat), the sensor will be expecting more emissions than it is getting. It may assume that the excess is going through a failed cat, hence the error.
Pingu

Gooseacre
Joined: Thu 10 May, 2012 19:18
Posts: 152

  M roadster S50

Re: Engine Warning Light

Post by Gooseacre » Thu 21 Apr, 2016 11:49

I got the impression from others that there are both pre and post cat lambda sensors. The suggestion is that the post cat lambda is reading too similar to the pre cat one hence reporting that the cat is not working as efficiently as it should.

Will certainly check for leaks pre cat.
2001 Z3M S54 LB64010 #10/73
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pingu
Joined: Fri 30 Apr, 2004 17:01
Posts: 3337

  M roadster S50

Re: Engine Warning Light

Post by pingu » Thu 21 Apr, 2016 14:42

Gooseacre wrote:I got the impression from others that there are both pre and post cat lambda sensors. The suggestion is that the post cat lambda is reading too similar to the pre cat one hence reporting that the cat is not working as efficiently as it should.

Will certainly check for leaks pre cat.
Looking at t'web, the S54 has a significantly different exhaust to the S50. You have two cats, one on each branch, with pre-cat and post-cat sensors for each. You also have a temperature sensor (Item 5)...

Image

There doesn't look like there are any joints between the sensors and the cats for the gas to leak out, so (I fear) it will not be a cheap repair as it sounds like you need a new manifold. If it's just a hole, you may be able to weld it. You could save some pennies if you go cat-less, but you will have to check the MOT emissions limits for your car before you do.



S50 Comparison
My M (S50) has two pre-cat sensors, one on each header branch, just upstream from the rear flanges (sensors not shown on the diagram). I have a single cat in the middle of the car with no post-cat sensors.

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Sorry for the confusion, but I didn't realise the two exhausts were so different. Every day's a school day :rtm: :) .
Pingu

Gooseacre
Joined: Thu 10 May, 2012 19:18
Posts: 152

  M roadster S50

Re: Engine Warning Light

Post by Gooseacre » Thu 21 Apr, 2016 14:52

Glad to be of assistance!

If I just need to replace the cats then the BMW price is >£1200!!!

Cat is the same as the E46 M3 - can get one off ebay for about £200
2001 Z3M S54 LB64010 #10/73
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Gooseacre
Joined: Thu 10 May, 2012 19:18
Posts: 152

  M roadster S50

Re: Engine Warning Light

Post by Gooseacre » Tue 24 May, 2016 20:35

Just an update - reset warning light - not come back on again
2001 Z3M S54 LB64010 #10/73
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Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2121

  Z3 roadster 1.9

Re: Engine Warning Light

Post by Del » Tue 24 May, 2016 21:13

Good news. Could have been something really straightforward like the cat(s) just getting a little "choked up" and just needing a prolonged higher speed run to get nice and hot to clear themselves. One can get a similar issue (sometimes worse) with modern diesels and their DPFs - often need a good 100 mile run to get hot and burn themselves clean. :)

Gooseacre
Joined: Thu 10 May, 2012 19:18
Posts: 152

  M roadster S50

Re: Engine Warning Light

Post by Gooseacre » Tue 24 May, 2016 21:20

You know I think you are right. I haven't been doing many longish runs for a few months - mostly station runs :(

Since light reset done several 100 mile motorway runs.

Never thought that was an issue except for diesels.

Fingers crossed
2001 Z3M S54 LB64010 #10/73
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Gooseacre
Joined: Thu 10 May, 2012 19:18
Posts: 152

  M roadster S50

Re: Engine Warning Light

Post by Gooseacre » Mon 11 Jul, 2016 20:47

Oh well...

Got 6 weeks clear - light back on. Am guessing the same but will go get the fault codes. Looks like I will have to bite the bullet on replacing the cat.
2001 Z3M S54 LB64010 #10/73
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