Can anyone explain or show me a link that unravels the art of diagnostics using fault codes?

Submariner1

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I am intrigued to know, how do they train MB engineers in diagnosis?

I completely understand one cant just run a diagnostic tool on the car and just replace the items that have associated fault codes. Cheaper to buy a new car lol :)
IMO it just helps identify the general suspect components. But some may fail because others higher up the sequence failed.

I get that logic.

What I am intrigued with is when it finds suspect items, is this just because they are just lower down the chain of faults or is it indicative that they are only marginally within spec.?

Or is there absolutely no problem with these items, its just that there is insufficient voltage or current for them to operate correctly?.

A good example to explain my query is when my battery goes low voltage, it produces the “ABS and ESP are currently unavailable - See Owners Manual” dashboard message.
.. and the Manual says Unable to completed the initial self check diagnostics. (I assume due to low voltage? ).
I also see a differentiation between “currently unavilable” and the “inoperative or visit workshop” the latter I assume means a unit is defective, or potentially dangerous.

The MBII then finds the following faults

A) if the battery is slightly low
- low voltage on x sensor, reccommended visual inspection on the
- rear right and left rear RPM sensors and the front left sensor.
( I have cleaned the front sensors and reluctor rings ... all were reasonably clean and cleaned up nicely, and the rear right reluctor ring is new, courtesy of a new wheel bearing and hub ... non related issue).

B) if the battery is more discharged in addition to the above I get these fails:-
- right door controller open circuit or short to additional locks ( it doesnt have this option)

C if very discharged in addition to all the above, i get :-
- left seat lumbar motor
- no CAN message from N/?? ( ABS control unit )

If you drive 10 feet the message dissapears, and one can clear the codes.
If you fully charge the battery on the CTEK you never get this message or any fault codes. Leave the car 2 days and you can get the message, and it clears and one can start the car again that same day with no message or fault codes.
Leave it 3 days and the car will start and the message clears, but will reappear and be self cleared the next time you start it.

Initially I suspected a current drain, its at 40 to 50 mAs , which Mobilo says is fine. I did notice that when the battery is very low, the Fluke when set on Max Min ( time monitoring ) can see 110mA at some time.
Visually I saw this twice, and it will spike for 4 or five mins and drop back to 50mAs.

This NEW MB battery is also odd, in that when low normally takes 10-12 hours to go into “care” mode, but sometimes only takes 4 hours. Likewise it seems to have no guts! Sorry I really do not understand battery terminology. By that I mean if it shows 12.6V just open the door and the voltage crashes to 12.3V purely due to a door sam Using 350mAs . Is that normal?

I am sure impatient readers will say say for heavens sake just change the battery ... er I just did that, and got a faulty battery: and then got another new replacement. Note the DOA battery passed the full MB battery test 2 x and only failed on the 3rd battery test. This one is now showing the same attributes. Hence my fear of paying for multiple battery tests.

The normal process would be to have the battery tested, note that costs more than the actual battery.
TBH to solve this ****ing irritating problem, I would even pay that, if I thought it would get to the truth of the matter.

I strongly suspect this battery is defective and came from a faulty batch. ( same month of mfg.! )

Ironically I have decided to let the battery drain down and when it fails to start, call Mobilo and get it replaced. And then if the problem persists, give it to an Indy.

But I was again thwarted by this dam battery. Last night all shut down, drain of 40 - 30mAs it was 12.5V. This morning its up at 12.7V! The thing is posssessed. Makes me feel some of the cells are intermittantly not connecting properly. Is that possible. (note the first new battery finally failed when 2 out of the 6 cells went short circuit?? ... imo could that explain why sometimes she goes into CTEK care mode so quickly).

Am I right in waiting till she fails to start and getting a replacement battery before spending money on looking for a fault? ( note the first battery caused the very same modules to fail ).

Sorry if this irritates some folks but I really dont want to spend yet another £156 replacing another new battery.

Just to rule out water damaged SAMs and wiring, I had the body shop lift out the front carpets including removing throttle level, and look under the dash, check blower motor was totally dry, check all the drains incl. sunroof etc. ( all OK) and in their opinion the car has never got wet inside, there was no water staining etc, just some light dust. Local MB body shop did that for £40 ... very reasonable indeed.:)

The only thing I havent done is strip out the old tracker, its in the rear wing ... passenger cabin side :(:( so a total pig to get at. Rear window door card .. not fun on a Coupe. Tracker say this can for a short time send a comms msg. Using 300 to 500 mAs or the normal 1 to 3 mAs.
Imam now considering this ... as its an element the Indy cant test .. no fuse to pull.

Leads back to my main question, when one is tryi g to irradicate an intermittant current drain ( say there is one?? ) where the hell do you start if you cant see a drain?
Pull a fuse and leave it 3 days to rule it out! Christ that could cost a fortune?

Or is STAR clever enough to monitor the car for 24 hours and specify any current drains and where they were?

Alternatively can one just leave it, I assume that won't do any harm? And wait till something breaks, then at least you have something to find/mend!

Note for the cynical.
It took my wife to remnd me if out problems with an A Class battery. Replaced it and then it kept failing to starts. Numerous battery tests on the new battery. £460 of diagnostic tests and they removed my specialist Satellite tracker as that was deemed the only logical failure point. 3 days later she failed to start. Totally ****ed off I bought another new bigger battery. Its run perfectly for 4 years!
Luckily the garage refunded my £460 ... without me asking ... good customer service. :)

So bearing that in mind ... I trust the intelligent ones, can understand my relectance to accept “its not possible to get 2 defective batteries on the the trot”.

Ergo, did I really suddenly get 3 failing level sensors, an faulty ABS control module, a fauLty Door Sam and a faulty CAN controller and a faulty seat INSTANTLY ALL AT ONCE .?
 
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Botus

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I think you would glean a lot by reading my posts, forget if the style rankles get the message

On your current issue

1)fully charge the battery
2)put the vehicle on a stable power supply
3)make sure its not running

now run complete diagnostics....

delete about 20 irrelevant faults, drive the car 2 miles start at step 1 all over again.... magically the car is 100% perfect. drive for 6 months do process all over again. NOTE: you may have a real fault but I doubt it.

STAR or the later far more comprehensive XENTRY, is I believe TOTALLY painting by numbers.... you need virtually no skills, it says this is wrong, this is where you'll find it, shows a picture and words on what to do, you keep going checking, wiring, modules, connections, till it says OK move to next picture.

Main dealer tech skills = NONE when painting by numbers doesn't work ring Milton Keynes till a slightly less incompetent muppet talks you through it, when that fails, talk to Germany and an engineer will go OH its software.... wait 6 months we already know about it.

If a grunt with a blow torch and a plunger can get £120 a hour, why would a good tech work for a main garage for £18?
Think about it !!!!
One can almost count to 10 and the other needs a degree in multiple sciences, IT, electrics, hydraulics, pneumatics and understand how to fix / work around the hideous basic design flaws some halfwit engineer put there (who gets >100k) only to have people look down on them coz they have dirty hands and a bad back.
 

Jim2

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Ah but there's nothing to beat a good tinker.
And it's a worry when you can find nothing wrong......all that suspense waiting for the next fault to declare itself !!!! :)
 
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Submariner1

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If only I could just drive it.

Went to dealers to get the missing boot clips.
Decided to reset the tyre pressure monitor as one front tyre was 3 psi under and one rear was 1 psi over.
That was accepted.

Drove there without messages, bumped into one of their Master Mechanics, he kindly said he would show me how to free the rear wheels i.e. not go into Park and apply EPB. Nice little trick.

Drove out no messages ... then 1/2 way home ... and these 2 warnings appeared C3EA0BAB-2FA9-4A9E-829D-5A3483514799.jpeg
And this
44561EDA-0817-4F2C-BDB5-31B8DA6B73DB.jpeg

Drove home fine with both these illuminated, stopped car and they returned, turned off car and went to restart
And got this

0A40D8AE-199F-46CF-A2DD-07146EF74BCC.jpeg

Oddly the car started this time without the usual “Abs and esp unavailable” msg.
And This appeared ... stupidly I thought great its sorted itself ha ha
Its a lovely weekend no way ... punishment is due

D8661E45-694A-4D91-881C-2277FCE6DFF0.jpeg

Drove few yards and the top 2 messages returned. :( weekend ruined )

My theory this was all due to undervoltage was jolted by checking the battery ... OMG the drive had charged her up to 12.7V .... bang goes the optimistic theory it just needs a new battery.

Other than at the start of the journey it recorded the battery voltage as 12.3V . Could thi have started it off? I would have assumed ince the alternator got the viltage up these issues would have gone away.

So frazzled by all this, for once I put in the MBII when the KeYless Go was inserted ( I usually meticulously use the key) . Hopefully it was off , As I had locked the car when I went inside to get the MBII. But I am now worried it was in position 1 but with the airbag sign gone! ( but dont think so).

Ran the MBII diagnostics and I now have this fault ... no idea what that is? Never seen that before.
1D16B503-51D1-4617-BF51-83FAFA748160.jpeg

And as usual BFF581AE-D2B6-47E9-8A50-D953FA2FDACF.jpeg
Oddly its now recommending I inspect all 4 wheel sensors .. previously just 3.
I have cleaned the 2 front sensors and reluctor rings, and weather permitting will do the backs tomorrow ... though I suspect they will be fine like the fronts were.

Rapidly failing out of love with this car. Think its payback for being disloyal, as I had a coursory look over a lovely 2016 S Coupe 500 AMG line for sale in the dealers, for £64,000 with 14,100 miles. And a 2 year warranty.
Luckily for my wallet the ESP Inoperative msg. Hadn't appeared by then, or seriously I would probably have bought it! ( after a bit of a barter!)

Oh well back to reality ..
And this fault four times ... seen this many times before
C111868D-7504-47C4-845D-5ED6FDF4F258.jpeg
( is this indicative the ESP control block is nackered? ... however I have seen Google posts where this was just one sensor!

And now I got this Parking brake msg. Once ! Couldnt clear it
But discovered it only happens when the MBII is connected??
1346C3D8-44B7-488B-954A-D92A6DF93E01.jpeg
And to top it all suddenly the car was doing 160mph in the driveway! In P

I should have entitled this thread C216 Nightmare ...

Appreciate no sarcastic stupid ... you should just drive it crap ... just not in the mood.
Any helpful comments very much appreciated.

Oh and I forgot to say once with the MBII connected when I tried to drive it the engine seemed not smooth, and the power steering went ****** stiff.
Once restarted that went away.


In summary the car is f*cked!
And a nice weekend to you all!

So much for the planned nice drive out for a good lunch and a big drink with swmbo driving home!
 

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Submariner1

Submariner1

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I think you would glean a lot by reading my posts, forget if the style rankles get the message

On your current issue

1)fully charge the battery
2)put the vehicle on a stable power supply
3)make sure its not running

now run complete diagnostics....

delete about 20 irrelevant faults, drive the car 2 miles start at step 1 all over again.... magically the car is 100% perfect. drive for 6 months do process all over again. NOTE: you may have a real fault but I doubt it.

STAR or the later far more comprehensive XENTRY, is I believe TOTALLY painting by numbers.... you need virtually no skills, it says this is wrong, this is where you'll find it, shows a picture and words on what to do, you keep going checking, wiring, modules, connections, till it says OK move to next picture.

Main dealer tech skills = NONE when painting by numbers doesn't work ring Milton Keynes till a slightly less incompetent muppet talks you through it, when that fails, talk to Germany and an engineer will go OH its software.... wait 6 months we already know about it.

If a grunt with a blow torch and a plunger can get £120 a hour, why would a good tech work for a main garage for £18?
Think about it !!!!
One can almost count to 10 and the other needs a degree in multiple sciences, IT, electrics, hydraulics, pneumatics and understand how to fix / work around the hideous basic design flaws some halfwit engineer put there (who gets >100k) only to have people look down on them coz they have dirty hands and a bad back.

Your style does not rankle ... begginning to think you are spot on!
 

Jim2

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Seems to be suffering from a multitude of dislocated idea's........ Sorry for your misfortune Submariner..:eek:
 

AMGeed

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Sorry Sub. Not trying to be sarcastic in my earlier message. It seems your CL is jinxed.
Get rid of it ASAP. You have had more problems in the last 6 months than I have in my entire 5 year ownership of my E class.
 
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Submariner1

Submariner1

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Before giving up on it totally. Tested the battery .... magically It had risen from 12.6V to 12.7V
So started her.
Up came the “ ABS and ESP not currently avialable” ( to be expected as it was there on shut down)

Drove her down the road 15 ft and that message disapeared, I was waiting for the ESP Inop. rubbish to appear as it had 5 times before ... nothing. No Parking Brake stuff either.

Thinking last time the “ESP Inop.” Msg. Stuff appeared it was on a 16 mile journey.
So drove her like she had been stolen for 29 miles ... twists and turns .
All perfect. Absolutely No Warning Messages.

So was it all actually due to initially starting with 12.3V i.e. too low.
Or
Is this a self healing car!

Totally beyond my logic!!

I will clean the rear Sensors and reluctor rings ... so I know that fault code is bollocks.
Then get Mb to change the Battery or buy one myself.
If it re-appears, then its off to my Indy.
 

om613

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My advice to you is:
Book a holiday, drop it at Star, PCS etc. with the instruction to conduct a 'full electrical system test', maybe there's a bad earth somewhere?

There's no point owning a car you or your wife can't trust.
If you like DIY and tinkering, which you seem to, get an older MB from the '80s?

** Just to add, NO they're not engineers, they're technicians.
 
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Submariner1

Submariner1

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Sorry Sub. Not trying to be sarcastic in my earlier message. It seems your CL is jinxed.
Get rid of it ASAP. You have had more problems in the last 6 months than I have in my entire 5 year ownership of my E class.

I differentiate jobs bringing her up to tip top spec ( which is virtually there ) and real problems.

But this, call it “under-voltage / electrical” problem, I agree it is an absolute nightmare. Hopefully its something simple like it only needs a decent solid Battery, and all will be fine.
But the way it presents the/these chameleon like problems, one minute like this and then like something different is scary.
And I hate it
 

Dell

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I know it’s not the same thing but I had lots of silly going’s on or not with my c class and it turns out that Merc had lots of problems with soldered joint not being done properly in the wiring looms,someone that worked for Mercedes told me what joint was dodgy on my car and it sorted five faults out just by this one soldered joint.
 

umblecumbuz

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Driving in a crowded city, I used to think that there's nothing more useless than a car you can't park.
Update: There's nothing more frustrating than a car you can't use.

As I've said before - such a car is just a tin box in which you pour money.
 
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Submariner1

Submariner1

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Driving in a crowded city, I used to think that there's nothing more useless than a car you can't park.
Update: There's nothing more frustrating than a car you can't use.

As I've said before - such a car is just a tin box in which you pour money.
Thats very true, and with ABS controllers at £1,062 or £672 MB refurbished and each sensor at £119 each? ( and the back and front are different so no cheap buy one as a substitute known good part lol) one has got to be sure thats the problem.

And others have said it could even be wiring! Or a dodgy earth.

Pretty convinced I need to sort the intermittant battery issue out first, as all ( or many) other issues could just be down to low voltage.

Star would definitely help ... but I wouldnt trust myself with that! Simply dont have enough lnowledge not to wreck something vital ergo expensive.
 
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Submariner1

Submariner1

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MBII says Under Adaptive Braking, RPM Sensor Speed, I noticed even stationery it shows exactly 0.40 mph on all 4 wheel sensors.
Pretty sure that was like that before my issues.
Is that something that could contribute to my issues and or should be corrected with STAR?

Driving at low speed the fronts seem about 0.5 mph faster than the rear sensors.
At 50 mph or more they are almost 1 mph faster.
I assume thats because I have staggerred wheels ... slightly different profiles .
Both left and rights seems virtually identical so I dont think the sensors are an issue?

Just ruling out anything possibly problematic
 

peterws1957

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My advice to you is:
Book a holiday, drop it at Star, PCS etc. with the instruction to conduct a 'full electrical system test', maybe there's a bad earth somewhere?

There's no point owning a car you or your wife can't trust.
If you like DIY and tinkering, which you seem to, get an older MB from the '80s?

** Just to add, NO they're not engineers, they're technicians.
^^I have to say Sub this is the way to go. Much as I enjoy tinkering with my 60 year old cars, (where I can fix virtually any problem with a half inch spanner or a length of wire) I quickly realised with the CL that its not the sort of car to tinker with. Get it with an expert on Star and bite the bullet! Otherwise I can see ulcers forming pretty quick:).
 

LostKiwi

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Sub, sometimes you over think things and make them more complicated than they need be.
Wheel speeds will never be identical front to rear unless every parameter is identical (wheel/tyre size, wear, pressure, tyre load etc).
If wheel speeds were an issue you would have the ESP light blinking away furiously as it tried to compensate for what it thinks is a wheel(s) that's lost traction.
 

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