Problem after new battery

mikrt

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2013 C220 CDI BlueEFFICIENCY AMG Sport Plus 7G-Tronic Plus 4dr
Changed battery from 6 year old original to genuine Mercedes same spec.

Now have error message on dash "Restraint sys. malfunction. Consult workshop" along with airbag light.

Have scanned it, code B2735-2B is there. It clears but returns straight away. Description is "The squib For Pyro Fuse 'On-Board Electrical Network Line' Has A Malfunction. The Electrical Lines Have A Short Circuit To Each Other. -Current, Pending, Stored"

Can anybody shed some light please. There are no Merc Indies I know of local in West Wales and not sure I'd trust anybody without Merc knowledge.

Thanks in advance.... again.
 

Smart320

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When I needed a new battery for my w211 E class I used Sinclair the MB dealer at Nayland, £140 fitted and no problems afterwards. Nearest Indi I know of is Continental Cars in Cardiff. Probably cheaper to go to Sinclair's!
 

grober

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The battery negative? connection has a pyrofuse unit [ little box]designed to fire if the airbags go off signifiying that the car has been in a substantial collision- this isolates the battery post-impact to prevent a fire in the damaged vehicle. I would assume this needs electrical power/signal connection to fire if required. I think the system is telling you there's a faulty connection to the unit or the unit itself has gone faulty when you changed the battery. Appart from checking all connections to the unit replacement is probably the answer. its important to disconnect/reconnect the battery terminals in the correct order to avoid damage
Disconnect = NEG then POS
Reconnect = POS then NEG

 
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mikrt

mikrt

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Thanks for replies gents. Grober, is this pyrofuse unit you mention part of the block which had the charging terminal on it, with the red slide cover?
 

grober

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Depends evidently on the age of the car- iirc it was once part of the block with the charging terminal/red sliding cover on it -if its faulty that whole unit may have to be replaced. I now think the little box on the negative terminal may simply be a battery voltage sensor not certain . Still pretty sure your fault is related to this pyrofuse wherever it's located . Don't think its fired off or your car would have no power- however the SRS system thinks its faulty for some reason and changing the battery may have precipitated this ???
 
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mikrt

mikrt

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Thanks again, I'll have a chance to check around under the bonnet on Tuesday.
I did wonder if a fuse had blown somewhere in the unit mentioned, but the short circuit mentioned in the description, rather than open circuit means I could have been wrong?
 
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mikrt

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Ah, I suppose a short circuit might have blown a fuse, maybe 1st guess was right after all.
 

kid-jensen

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Had the same error message when I changed my battery.

Just cleared the message and it stayed cleared...
 

Dave Richardson

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Have the same problem on our CL203 & it was the fault was cleared

D
 
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mikrt

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Problem solved!
Issue was loose yellow/blue connector on the side of the positive post. I must have knocked it loose and damaged the clip while re-fitting the battery. I should have got the Mrs to hold the leads out of the way.
Screenshot_20190709-125220_Gallery.jpg
 

Uky

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I was given the following advice when replacing the battery in my E350 (C207)
by a friend who works as a professional MB mech:

1. Open the bonnet.
2. Close all doors but leave the driver side window open.
3. Lock the car.
4. Remove all keyfobs away from the vehicle.
5. If keyless entry: Do not touch the handles.
6. Wait some 30 minutes for the car to go to "sleep-mode".
7. Disconnect the battery according to Grober (above).
8. While you are at it - remove the battery plate and clean the area from any old leaves
or other dirt. If an E-class coupé (and possibly others) Be aware that one of the bolts
holding the battery plate is right above an aluminium tube. Be sure that you use the same
short bolt when putting the battery plate back!.
9. Reconnect the battery.
10. Unlock the car. (etc)

This will ensure that you do not lose any calibration and that the control system gets a fresh
start without setting any DTC's.

(Should there be any problem, the window is open and the driver compartment is
accessible.)
 

dan-mb

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Get the car scanned on MB STAR and have it checked; should be able to clear the faults after. A battery change can throw up errors for no reason. It's a guessing game without a proper diagnostic.
 
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mikrt

mikrt

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Just to be clear, thanks all for the advice.
But the problem is solved.
It didn't need star, the error message is cleared.
It was just a loose connecting, nothing wrong with the battery either.
 

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