pre-safe inoperable C220 diesel 2012

[JD70]

Hi all, I'm new here and not sure if this is the best place to ask but here goes..............thanks in advance for any info/help you might be able to provide.

When I switch on the ignition and start the engine, "Pre-safe inoperable" is displayed (and the front seat belts don't 'auto-tension', which might be a red herring).

Any thoughts as to how I might test any specific parts of the car before booking it into the Mercedes dealer for them to assess & fix? (sky high initial charge of £175)

 

[mioba]

Does it go out after some time of driving. The reason I ask os beacuse some pre safe bits are dependent on voltage.

 

[Tony Dyson]

Beg, borrow, buy or steal a good quality OBDII reader capable of reading all the modules in your car, it really is an essential piece of kit for today's DIY mechanic, a voltmeter would be a good start to check your batteries!

 

[JD70]

Does it go out after some time of driving. The reason I ask os beacuse some pre safe bits are dependent on voltage.

Hi and many thanks for responding mioba.
The message appeared for the first time yesterday (3rd Feb 22). As it included the word "safe" I thought I'd better investigate asap; hence the post I placed yesterday. LOL, today the message hasn't (yet) appeared but all the same I've taken voltage reading across the prime +ve battery terminal & earthing body post as follows. I'd appreciate it if you'd comment on the values and if they're 'odd' please let me know what you suggest I do now

12.21 v - ignition off, all services off
14.93 v - engine running (for a couple of minutes) but all services off
14.88 v - engine running all services on but A/C off
14.87 v - everything on

 

[JD70]

Beg, borrow, buy or steal a good quality OBDII reader capable of reading all the modules in your car, it really is an essential piece of kit for today's DIY mechanic, a voltmeter would be a good start to check your batteries!

Hi and many thanks for responding Tony.

I've posted above the voltages across the prime battery as of this morning. I'd appreciate your thoughts please?
Also, do you recommend any particular model of "good quality OBDII reader" please? If possible, I'd prefer to have a reader that a novice can use and provides results in easy-to-read non-technical format if possible?

 

[Blobcat]

Hi and many thanks for responding mioba.
The message appeared for the first time yesterday (3rd Feb 22). As it included the word "safe" I thought I'd better investigate asap; hence the post I placed yesterday. LOL, today the message hasn't (yet) appeared but all the same I've taken voltage reading across the prime +ve battery terminal & earthing body post as follows. I'd appreciate it if you'd comment on the values and if they're 'odd' please let me know what you suggest I do now

12.21 v - ignition off, all services off
14.93 v - engine running (for a couple of minutes) but all services off
14.88 v - engine running all services on but A/C off
14.87 v - everything on

Alternator working fine, battery is pretty much knackered at 12.21v - should be >12.4V at rest

 

[JD70]

Alternator working fine, battery is pretty much knackered at 12.21v - should be >12.4V at rest

Ah, many thanks Blobcat. Both batteries are the originals, so do you suggest I replace both batteries or just the prime battery?
Also, would you buy direct from Mercedes or somewhere else, and if so where, please?

 

[Blobcat]

Ah, many thanks Blobcat. Both batteries are the originals, so do you suggest I replace both batteries or just the prime battery?
Also, would you buy direct from Mercedes or somewhere else, and if so where, please?

Tanya batteries (website) gets good reviews here - Varta are a good make
Mercedes Grangemouth (do forum discount) and will deliver for ~£5

 

[Tony Dyson]

Hi and many thanks for responding Tony.

I've posted above the voltages across the prime battery as of this morning. I'd appreciate your thoughts please?
Also, do you recommend any particular model of "good quality OBDII reader" please? If possible, I'd prefer to have a reader that a novice can use and provides results in easy-to-read non-technical format if possible?

Main battery is shot as previously suggested and needs replacing, aux battery is personal choice, if voltages are within parameters then whether you are a "If it isn't broke don't fix it or a may as well before it finally gives up the ghost" is your choice!
OBDII readers, search the forum there are many threads on the subject, Autel and iCarsoft are popular choices and there are many options available, especially with iCarsoft, there are MB specific readers and slightly more expensive multi brand readers if you have other vehicles to maintain, make sure you buy from a UK authorised retailer as there are many ebay suppliers selling cloned models which the manufacturers will not support with their regular updates. Lots of information here https://ljmcardiagnostics.co.uk/
A novice can use any OBD reader, the clever bit is interpreting the reported fault and identifying what failing component or symptoms have created it? But I'm sure members will help with feedback if you were to post the readings and request assistance?
Is this your battery? https://www.tayna.co.uk/car-batteries/varta/f21/

 

[daibevan]

Welcome. Everything I was going to say has already been said. Mercs don't like a low voltage from an old battery.

 

[JD70]

Excellent, many thanks to all of you. I think I've got the info I need to arrange for a main battery replacement and check the aux along the way.

Brilliant, thanks again everyone