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Evening. I've got an 08 S550 in mint condition. The SRS light just came on and in lieu of going to the dealer and Just for the heck of it I purchased one of those Icarsoft scanners to attempt to read the code and to my surprise I was able to! It reads "undervoltage at terminal 30". Unfortunately I have absolutely no idea what this means or even where to start searching for problems. Both batteries, the starter and consumer batteries as well as the alternator have all been replaced within the last 2 years and are functioning perfectly... in other words no known voltage issues on the car. I am really stumped on this one any advice would be greatly appreciated. I thought that perhaps it might be the child sensor mat on the passenger seat but I would think this code reader would reveal that as a problem maybe it's just not sophisticated enough. Thanks in advance
there would have been more to that code than just those words - the gibberish at the start is vital
if you have low volts these model Merc throws teddies out the pram and stores stuff in diagnostics memory for fun - however air bag lights usually indicate a real fault, not confusion - before I got mine it had a scuffed bumper the sort of thing that most would polish out rather than repaint but it was enough to upset front left chassis leg crash detector
for two years the light was intermittent but would clear for up to to 9 months... however always came back if not driven for a few weeks and the battery got slightly low - when someone told me what sensor the gibberish code was, and where its hiding, 30 mins and $50 later I had fitted a new one - never seen the light or airbag error since (that was more than 5 years ago)
seat belt buckles, or seat pad switch heavily worn is in a normal driver on older Merc models to bring in the air bag light
Thank you for the reply and you are correct I'm still trying to learn how to use this scanner and there's actually 14 codes related to the SRS! Most of them are redundant repeats but there's 5 actual codes and I will post them when I get home. It will not let me delete them and my understanding is you can't delete them until you fix the problem maybe by posting the actual codes verbatim verbatim with the gibberish someone will know what the fix might be.
real faults won't appear to delete as they return straight away but usually when u buy a car it might have 10 years of lies stored in diagnostics - delete the lot - go for a drive for 10 mins and real one's will be straight back
never waste time with any OBD menu options in these tools - is a very basic emission only data set from the days of fred flintstone
the best bit is a shadow memory no one talks about - some scanners find both and continually lie about rubbish you can't remove and might have been utterly irrelevant for many years - if the car ever had software updates on certain stuff it can throw the entire car's multiple canbus networks full of fake noise as its taking some offline to write the software - then it comes back with every fault possible stored in the shadow memory - It a secret stash the developer might care about when making the car or in the first few years of life as they seek to obtain info from customer cars for bugs they struggled with. But leaving this full of useless junk after major programming sessions is silly - its no use to anyone.
my autel kit reads both areas on the car - deleting the junk shadow memory took scanning from 35 mins to 5 on my MOT Pro diagnostics - but only dealer kit with developer mode enabled can get at this (as far as I know)
I completely understand and agree with what you are saying I actually found codes in other areas like air conditioning braking ng and Ignition which I was able to clear these were codes that could have been years and years old. So at 1st I thought it was the child seat sensor mat censor Mat but here are all of the codes currently reading verbatim.
-Undervoltage at terminal 30 -Undervoltage at terminal 15R
-No CAN message was received from control unit A1
( Instummet cluster)
- No CAN message received from control unit N93
( Central gateway control unit)
-Control unit N2/7( Restraint systems control unit) is defective)
- The key ID stored in control unit N2/7 (Restraint systems control unit) is not identical with that received by control unit N73. (EIS [EZS] Control Unit)
Any advice or guidance would be greatly appreciated I'm just trying to avoid going to the dealer and getting raped.
The key ID stored in control unit N2/7 (Restraint systems control unit) is not identical with that received by control unit N73. (EIS [EZS] Control Unit)
that sounds a bit like a different part was fitted incorrectly and or is incompatible - so much of modern car manufacture is trying to make exchange of second-hand parts - hard work
as its free "and can help a muddled car get over itself " - try taking the battery off for 20 mins and see it it wakes happier - the fault would still be stored but might not be valid any more....
Thank you I will absolutely try that.. disconnect both consumer and starter battery. I purchased the car CPO and have owned it ever since so there hasn't been any rogue parts installed I'm aware of period. I'm pretty stunned I just called the dealer for the heck of it they want $250 just to hook it up to star and tell me what's wrong!! So I definitely don't feel like I'm wasting my time figuring it out on my own at this point. For me the one that says says there is actually a defect is the more enlightening code but I have no idea what this means. I've got it posted on some other chat sites but no one has replied. Will definitely report back
on pre 2007 car with twin batteries (massive 25kg hidden in the boot) unlock - key out - open boot - lift floor trim, right of spare wheel centre, is an earth strap and 13mm headed bolt with red paint - undo and leave clear of the body - reconnect after 25 mins - redo all four window and sunroof anti trap feature - see if fault will clear in diagnostics
All German cars can't be fixed without an understanding of the confused madness of overly complex build they introduced from 2005
The EU upset the protectionist practices - making it illegal to not share comms and ability to repair outside the crooked main dealership network - que - everyone can now steal the car via OBD port - likely the real reason to introduce the change
So all dealers on nearly any car now have 150 to 300 dollar charge before they will entertain what might be wrong
the joy of canbus - insane wiring and control by a lunatic that only dealer tools can communicate with - half of the software is random confusion of security bugs,
VW peddling new cars with libraries that were outlawed in a windows machines 10 years ago
The factory wifi code saved inside Fords ECUs !!!!
GM hack the car put the brakes on unfixed for 7 years even though they knew all about it
BMW opened entertainment system to white hat hackers and inside a week they'd found 40 security vulnerabilities
USA trying to kill competitor brands
1980's fake inadvertent acceleration on Audi nearly wiped VAG off the plant
2014 fake inadvertent acceleration on Toyota - NOT a single car had a software fault (one US policeman committed suicide and two grandads had wedged the floor mat under the pedals)
I remember all of those stuck gas pedal accidents every one of them was human error...... Either pedal confusion, stuck floor mat or other human error! Anyway I disconnected all battery power from the car and left it for about 3 hours unfortunately all the codes are still there and nothing will clear. I can't believe someone out there in Mercedes land hasn't had this problem or that someone out there, perhaps a Mercedes mechanic, doesn't know what these codes mean? I have a 30 year old vintage Ferrari 1992 model that has a primitive code system which consists of a series of blinking lights......very difficult to decipher the codes.......but I was able to post the code on a Ferrari chat forum and figure out the problem and narrow it down to a faulty throttle potentiometer....cost $26 to repair car! Hopefully someone out there in Mercedes land has had this same problem.
its great you are trying - but the dealer tools have idiot guides to tell you where next to try and find something mind boggling, once past the basics - I would NOT discount the text - its often a bit random - but often has clues that make far more sense when you actually found what was wrong and fixed it
Just had a thought - if your voltage is under 12.1v as you scan - it will burn 35 amps key on, engine off, and a new battery can die in 25 mins no problem. If your voltage is low you might be finding gibberish that leads you astray - lots do with the engine running - but its not supposed to be - again here its random, if you scan everything with it running you should hear the car have a moment as the engine ECU is interrogated - goodness know what damage one might do - other stuff might be OK with it running, but I remember my snapon one saying don't play with the roof module if its running (OCP) !!!
Safest to have the engine off and turn off lights, heater fans - and ideally - always have a battery support unit holding the volts above 12.5v if making prolonged attempts at check things out
three things
1) I suspect the manufacturer didn't really know what they were building on this model - a few retiring nut jobs went mad, then left and the children have been making it much worse ever since
2) the dealership employ sacked McDonald workers who are completely out of their depth pumping up the tyres let alone following the idiot guide
3) there are some great independent specialist garages out there but they service E classes and don't see many of these then steer well clear
this list with the code upfront would be better, lots stands out to me as something you need to understand / fix - no volts, no can signal could be wiring fault or failing module but this says to me you have a hookey unit faking it badly and the car says NO !!! " The key ID stored in control unit N2/7 (Restraint systems control unit) is not identical with that received by control unit "
But checking your reply when I flagged this before you say you've had from new and its all legit - then I'd start off looking at the SAMs - squirrels / mice eating wiring looms, and or to see if the front one has been taking a bath - a common issue Mercedes engineered where the sunroof and screen drains don't function a week after selling the car.
- Undervoltage at terminal 30 -Undervoltage at terminal 15R
- No CAN message was received from control unit A1 ( Instummet cluster)
- No CAN message received from control unit N93 ( Central gateway control unit)
- Control unit N2/7( Restraint systems control unit) is defective) - The key ID stored in control unit N2/7 (Restraint systems control unit) is not identical with that received by control unit N73. (EIS [EZS] Control Unit)
see attached a few pics of what's what and where, (I'm NOT saying its a fuse, hardly likely) - but power to from / to this module messed up YES.... why ??? .
Front SAM
Fuse F61 7.5amp SRS Airbag Restraint System N2/7
Fuse F37 7.5amp EIS Control Unit N73
Sheet 2
Central Gateway Control Module (N93) Left front upper footwell.
Thank you for the lengthy reply. In my mind the solution is staring me right in the face with this code
:-Control unit N2/7( Restraint systems control unit) is defective)
it says in no uncertain terms that it is defective but what the heck and where the heck is it? Where and what is Control unit N2/7. Again I just can't believe that there aren't Mercedes mechanics or people that have had this problem on this forum... it's mind boggling!
I think OP or some IT anomaly got muddled on the ETC query seems to be replies to this one
Originally Posted by Polo35m
Thank you so much for keeping this thread and my hopes alive! I did read on another forum that the cupholder which is directly above the unit is subject to getting wet due to spillage or condensation from cold drinks over time so I'm going to pull it out see if I see any noticeable water damage I will definitely report back ASAP! Thank you again!.
PS Any idea where the fuse location is for that control module?
Sorry I accidentally scrolled all the way down and have been replying in the ETC thread. Anyway I pulled the relative console pieces out and inspected the module and it is Palm Beach Pefect....squeaky clean ...no evidence of water damage whatsoever. I'm ready to throw in the towel and take it to the dealer. Tired of dealing with it....certainly gave it the college try.
I just wanted to revisit this thread one more time before I take the car to the dealer and get ripped off. An important bit of information I left out in the beginning was that I had removed the start button sensor for cleaning and when I put it back and started the car that is when the SRS light came on. Maybe this is relevant maybe someone out there might have a explanation or fix for this. Finge4s crossed.
a dealer will almost certainly be no help whatsoever - they will plug it in and start throwing parts at it with no idea which one it needs - probably till you run out of money and don't darken their doors again.... an indy with decent kit and experience how to use with bearable prices and maybe some history working on these old cars is about 9 million percent more likely to help
07-29-2022, 10:41 PM
