SRS issue b48/2

[Tony.Brown]

Hi all, hoping someone here can point me in the right direction, I have an SRS light on my old 2008 X164 GL320 CDI right hand drive, which my NT510 Elite scantool reports as "fault in communication with component B48/2 (Passenger side frontal acceleration sensor) or there is a cable fault"
I have replaced the sensor (003 820 2926) with a good used sensor, but after clearing the code, it immediately shows again.
In an attempt to find a break in a wire I've used an oscillating probe to trace the cable from the sensor back as far as the firewall, but I'm unable to see where it goes from there, even from under the car.
I'm now beginning to doubt the sensor, which I will swap with the drivers side to see if the problem follows the sensor as soon as I can, but would like to know if there is any way to test these with a multimeter?

Could this be a misreported fault?

Any and all help appreciated!
Tony.

 

[Wighty]

Hi all, hoping someone here can point me in the right direction, I have an SRS light on my old 2008 X164 GL320 CDI right hand drive, which my NT510 Elite scantool reports as "fault in communication with component B48/2 (Passenger side frontal acceleration sensor) or there is a cable fault"
I have replaced the sensor (003 820 2926) with a good used sensor, but after clearing the code, it immediately shows again.
In an attempt to find a break in a wire I've used an oscillating probe to trace the cable from the sensor back as far as the firewall, but I'm unable to see where it goes from there, even from under the car.
I'm now beginning to doubt the sensor, which I will swap with the drivers side to see if the problem follows the sensor as soon as I can, but would like to know if there is any way to test these with a multimeter?

Could this be a misreported fault?

Any and all help appreciated!
Tony.

I had this fault on my W211 , it turned out to be low battery , mine was 10 years old at the time . A new battery sorted it .
I do vaguely think I’ve heard that you need to swap the sensor for one of the same make (but don’t quote me)

 

[Tony.Brown]

Thank you Wighty for your reply, I should have mentioned that the battery is only three weeks old and the sensor is the same MB part number as the one removed.

 

[Wighty]

Thank you Wighty for your reply, I should have mentioned that the battery is only three weeks old and the sensor is the same MB part number as the one removed.

That’s me all out of suggestions ..good luck buddy

 

[Botus]

a good used ? - they sell them in the dealership new with no faults for peanuts - how can you tell its good?

mine needed one, a tiny bump on that corner that almost didn't need paint caused it to give up - 7 years on its replacement has never shown up again (sort of in line with what wighty says - its used to go away for a bit if you charged the battery - but once is was changed, the battery can be anywhere it wants the fault is never there now)

all that said "cable fault" is not the same as, the acceleration sensor is not happy

 

[Tony.Brown]

Thank you Botus for your reply.
If you speak to any good technician, they will tell you that throwing parts at a problem is a waste of time and money, codes are not always pinpointing the problem, merely a symptom of the cause. Testing and diagnosing the exact problem is the best practise.

You ask "how can you tell its good?", which is my question, "any way to test these with a multimeter?", do you know if they can?

I do not know what the test values are, or if this is a misleading fault code or not, which could be something else entirely.

Peanuts? Maybe where you live, but not here in Australia, my closest MB dealer is over two hours away, the used part was not only local, but very inexpensive.
Perhaps it is no good, which is why I asked if there is a way to test it
Tony.

 

[Botus]

you could swap the left for the right chassis leg and see it the fault moves sides....

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[Tony.Brown]

Is it correct that a new sensor requires SCN coding in order to recognise a new part?

 

[Wighty]

Thank you Botus for your reply.
If you speak to any good technician, they will tell you that throwing parts at a problem is a waste of time and money, codes are not always pinpointing the problem, merely a symptom of the cause. Testing and diagnosing the exact problem is the best practise.

You ask "how can you tell its good?", which is my question, "any way to test these with a multimeter?", do you know if they can?

I do not know what the test values are, or if this is a misleading fault code or not, which could be something else entirely.

Peanuts? Maybe where you live, but not here in Australia, my closest MB dealer is over two hours away, the used part was not only local, but very inexpensive.
Perhaps it is no good, which is why I asked if there is a way to test it
Tony.

I agree with the throwing a cheap part at it from a diy perspective. My specialist is over an hours drive away from me , if I drive there I basically lose the day .
If I “think” from my diagnosis or research I’m in the right ball park and the part is cheap or might need replacing in the future anyway I’ll change it and see what happens . Occasionally I’m wrong , but hey ho it was a cheap part .

 

[Botus]

Is it correct that a new sensor requires SCN coding in order to recognise a new part?

no - just bolt the new one in - lots of misconceptions about this sort of thing in general on cars.....

a few, usually major bits that hold the mileage or the chassis number do need decent kit to write the info correctly to a replacement part- quite obviously if its a part of the engine immobiliser circuit (cluster, engine, gearbox etc.) then it makes sense most can't get at it

but others parts are designed just to be a cosmetic warning, or to block its functionality even when set up is not adjustable - they do it just be a nuisance, to help them fleece money - whats disgusting is they pretend its a theft / security measure - but its just theft from the user - all the thieves and scum know how to circumnavigate, so its just the legitimate user that gets mugged. The very one that could hand money to the dealership - so they make sure it happens... but then you are poor so have to pay for other services cash in hand.... and this isn't just the manu trying to rob you, its really robbing society and growing the black market economy - which as it happens is exactly the behaviour the corrupt government it trying to land !

next level is legitimate set up (for stuff like Body Control Modules - SMAS in Merc speak) AKA parts that must be set up to have the correct functionality. AKA coded to the specific vehicle / or to configure stuff to suit different regions regulations, to enable on or off toys that are optional on a given model and can be turned on off or have different functionality (like the sick moving chevron trash indicators they fit on"higher spec" models) - again this needs to be high end tools because we can't have every idiot turning off or on exterior lights lamps or switching on features that maybe unsafe as other elements aren't fitted on a given car.

then you have user re-settable bits - her ford (after the battery is taken off) should be started with the AC and lights off and allowed to idle from cold till the fan cuts in - to somehow reset the throttle body adaptions .... other ones like safety circuits, windows and sunroof anti trap cut outs etc. need to be re-enabled

most sensors or parts are just a replaceable item

For this airbag sensor I forget if the error just goes away for the user- and even here the user viewable nags often go away on most faults if the last three key on / off and sleep cycle has not seen the same error - but just aid theft, waste time and confuse - it often stays in the vehicle diagnostic list of useless detritus - as another societal collapsing opportunity - its so the garage can scare owners, printing off pages of horror stories at the next garage visit and they can ideally grab another 500 you can't afford, as its helps that black market economy flourish in the long term

 

[Tony.Brown]

Update, sensors swapped after removing headlamps and undoing the bumper cover, fault is still B48/2 no matter which sensor is plugged in, so not a sensor fault.
Now to work my way back toward the module in the centre console I believe?
I have read in other models that the pssenger occupancy mat can cause this code, does that sound right when it specifically singles out this sensor?
A problem further "upstream" maybe?

 

[ajlsl600]

Modern car, crxp electrics, hrs, weeks of headaches, pts made by lowest bidder and changed as soon as lower bidder comes along, outcome, owner gets shafted,
Sorry bud. Just imagine costs of taking that to the dealer hope you end up with low cost outcome. Good luck.

 

[Tony.Brown]

Modern car, crxp electrics, hrs, weeks of headaches, pts made by lowest bidder and changed as soon as lower bidder comes along, outcome, owner gets shafted,
Sorry bud. Just imagine costs of taking that to the dealer hope you end up with low cost outcome. Good luck.

I will persevere. It was mainly bought to offset boredom in my retirement, and so far it has succeeded!

 

[ajlsl600]

I will persevere. It was mainly bought to offset boredom in my retirement, and so far it has succeeded!

For sure. There, won't be many bored owners of ten Yr old benz. Always, somat doin it's best to drag one to the dealer avoiding that a constant trial

 

[Botus]

I wonder if the car isn't getting over itself when trying the swap - do you have a decent scan tool ?

how big was the bump that caused it to come up ? some modules that think they had to fire pre-tensioners or the airbags don't get past the capacitor charge up bit

re the other idea on seat occupation - this is a common bit of fun - wires falling off or seat belt buckles isn't it ?

have you triple checked for free airbags ? Oz are really into beating up the manus after the takata airbag disaster... and Merc have been very naughty

Mercedes-Benz failed to initiate a recall of some vehicles with faulty Takata airbags

The ACCC has accepted a court-enforceable undertaking from Mercedes-Benz Australia/Pacific Pty Ltd (Mercedes-Benz), after Mercedes-Benz acknowledged it had failed to initiate a recall of certain C class and E class vehicles with faulty Takata airbags, due to spare parts availability, in...

www.productsafety.gov.au

 

[Tony.Brown]

No bump, just hopped in the car to drive home and the SRS message lit up.
No airbag recalls show up on the Australian MB site, do they use Takata airbags?

 

[Tony.Brown]

Scantools are Foxwell NT510 Elite and Xtool A30M, still trying to work out which is the better one.

 

[Botus]

scan tools come in multiple flavours - autel do very good multi-brand ones - if you want to go single brand icarsoft mb3,

I'm not aware of stuff the mb3 does the autel can't do and for 79 other car brands too

the next step is two way comms which can code basic stuff to on or off - if its getatable - (mostly not on merc - boring) or to make an injector happy after replacement or such - this ability tends to come with is a three fold leap in price point

its doesn't really matter what you buy the next day you'll find it doesn't do what u want - I have full on xentry DOIP and can programme stuff with it - and get any flash file, but as it can't go online to Merc I can't finish off any SCN coding insanity they hide from the manual coding choices (of which merc does more hidden playtime in the background than yes no steps you can manually muddle up and destroy it)