OBD2 monitoring disabled?

[dldb]

Just picked up my new second hand CL 500 and have been reading the codes.

Seems there are two ECUs to choose from - $7E8 CAN-ID ECU #1 and $7E9 CAN-ID ECU #2, what is that about?

Anyway ECU 1 has far and away the most info and it says "Distance since diagnostic trouble codes cleared - 160KM" which is 28 miles before I collected it (ECU 2 says 65,535KM since cleared).

That wouldn't worry me unduly as no codes are currently showing and EML light is off HOWEVER further down on ECU 1 info it lists a load of monitoring which is disabled, notably misfire monitoring is off (but it does say later on "misfire monitoring completed") see pic below. Is that normal and should I somehow get them re-enabled?


There are also some OBD2 monitored test results warnings ('fails'): TID $81, 82, C8 and 86. My code reader just says 'values defined by manufacturer'. If anyone knows what this is about that would be great, thanks

 

[dldb]

I should add there are some minor apprarent issues - exhaust leak which I knew about and need to repair the patch, got a low coolant warning and topped up coolant with half a pint, seems ok at the moment, and just noticed what I thought was a slightly lumpy idle on starting which I hadn't picked up before (hence my concern about misfire monitoring). It's difficult on a V8 to detect.

 

[Botus]

what age is the car 2000 to 2005 ? if so I have no idea what you should see but scanmaster is by WGSOFT ? a german guy that does a good BMW motorbike scan tool... but then he went and buggered it all up creating is own list of codes rather than the std merc output?

anyway.... crank sensor will get a wobbly idle and like to fail on old cars... and what kind of coils / coil pack do these ones have... they don't last long on modern cars either

and of course a coolant leak and low rev misfire could mean head gaskets.... whats the oil and coolant cleanliness look like?

 

[mioba]

i guess its - CL500 (C216) 2009 107K miles 5.5l V8, going by the profile of the OP

 

[Botus]

well if its effectively a w221 coil packs and crank sensor def likely to be playing up
and I think I'd put that scanner in a skip, sounds like it talking utter rubbish

 

[dldb]

Thanks. Oil and coolant clean and no excessive steam in exhaust, have done 70 miles since picking it up so hopefully there is no head gasket leak.

Does the make of OBD2 reader mean I could get duff codes? I was expecting the ECU to send out the codes and not for them to get corrupted on receipt by the scanner, no matter how cheap.

I guess my worry is: Is it possible, with an expensive OBD2 tool that a dealer might possess, to disable misfire monitoring via the tool in order to hide problems from the buyer? Second question - is that what my scanner is showing or perhaps is the ECU clever enough to enable and disable misfire monitoring automatically, when it needs to?

I suppose I could always disconnect a plug and see what the scanner shows then. I might wait until I have a few more miles in the car.

 

[dldb]

The post above is my main query, please look at that first but below for info are the Monitored Test Results fails. I thought about putting them up as a new thread but it is connected to this post I guess.

Ignore the 'Lost communication' error, not relevant (I think).

 

[supernoodle]

OBD2/EOBD exists along side the diagnostic services that a dealer/professional tool uses. The former uses services numbered $01 to $0A, the later services $10 to $38.

OBD2 is there to allow independent vehicle repairers and authorities access to a set of standardised emission relevant faults and data.

What your tool is showing is not rubbish, but just is bit harder to interpret due its generic nature.

The modules that respond to OBD services will only be those the manufacturer has deemed to be emission relevant. Here the responses you got, 7E8 and 7E9 are ECU and TCM I expect.
On CAN, when a module responds it uses the ID of its physical address +8. So when you talk to the ECU you use CAN ID 7E0, and it will respond with a message with an ID of 7E8.

The monitors are a set of tests that the manufacturer deems relevant to say that system is working. Primarily the for the US as they don't do any tailpipe testing, just read these test results.
So for EGR/VVT it might be airflow drops by X when egr is opened etc. Clearly if the car doesn't have EGR or VVT that monitor is marked as disabled, whether it's then marked as completed or not is irrelevant.
It might be that there is no way for the ECU to test a system, that too would be marked as disabled.
If they are enabled and they don't pass that's a sign something in that system isn't quite right.
That's when you could use mode $06 and the TIDs and MIDs. They are the individual tests mentioned above. If course if they are not decoded they aren't very helpful. Note though, many tests won't complete until a particular temp, speed load is seen.

Note, there are two groups of monitors, tested since last clear (DTC clear) and tested this drive cycle. The former is the more useful.

Saying all that, you could do what most do and just ignore all this and just wait for a DTC to pop up.

 

[dldb]

Thanks my concern is that a DTC won't pop up if/when I get a misfire because the misfire detection may have been disabled, perhaps deliberately.

Looks like I will have to pull a plug and see what happens.

 

[V6Matty]

I’d suggest getting a more suitable scanner that deals with Mercedes, the iCarsoft range is very good MB3 being the current version, but you will be able to pick up an MB2 second hand now for reasonable money and will cover the 216

 

[dldb]

To be honest I prefer a PC based scanner to the purpose built ones. I'm sure the hand helds are good but they do remind me of 'educational' toys from my childhood. Also, as the codes come from the ECU not the scanner, the only difference I see is that my scanner may have different or no descriptions for the codes. It should still receive and show the same code as a £200 MB2 does.

 

[V6Matty]

That’s the point, if you are receiving different codes from the car because your scanner can’t interpret the signals then you’ll end up chasing something that isn’t a correct, ending fixing by throwing parts at a car

 

[dldb]

I don't believe my scanner will give me the wrong codes, worst case is it will give incorrect descriptions or no descriptions for the codes. Or are you disagreeing with that? I can live with no/wrong descriptions as I can always Google or search forums for the codes.

Having said that my Scanmaster ELM is quite good. It does pick up Mercedes specific codes - you can set it for make of car. It has been good with Opel and Honda cars for me too.

 

[V6Matty]

I suspect you’ll actually end up with spurious codes if any sometimes

 

[alexanderfoti]

I think there is nothing wrong with your car and you are trying to read monitors that are disabled on ROW configuration, as above, these are usually only enabled on USA cars.

If you really want to check it, unplug a fuel injector or coil pack and run the car.

 

[Botus]

if u bought a 216/221 then merc suitable diagnostics will be essential... as above OBD2 is basically a waste of space and on merc and a BM the amount of manu specific diagnostics that comes down that port is extraordinary

all the way down to telling you the mirror heater has popped on the passenger side and the bulb on the cigarette lighter isn't working etc.

not all kit is created equal for pre 2012 cars autel, will tell you everything wrong on the 221 almost as well as dealer kit for 150 quid - in most ways its easier to work with to boot - whereas as a 4k Snap On one still doesn't know what 8 modules do on the interior toys

 

[AnthonyUK]

I don't believe my scanner will give me the wrong codes, worst case is it will give incorrect descriptions or no descriptions for the codes. Or are you disagreeing with that? I can live with no/wrong descriptions as I can always Google or search forums for the codes.

Having said that my Scanmaster ELM is quite good. It does pick up Mercedes specific codes - you can set it for make of car. It has been good with Opel and Honda cars for me too.

No offense but an ELM based scanner is only going to read very basic and generic codes so it works on all cars as by law they have to support it and then it will only be for the ECU.

Your MB likely has 15-20 control units that an MB specific unit would be able to read.
I have access to a number of PC based packages but still always keep an iCarsoft (i980) unit in the car.
I agree it looks pathetic but has a pretty impressive set of features at least for my car

 

[Botus]

Your MB likely has 15-20 control units that an MB specific unit would be able to read.

depending upon spec a 221 / 216 will have between 45 to 62 different ECU's / modules, all sending lies and gibberish around the canbus. They generally try to throw a tantrum every drive