Keyless Start issues CLS55

[triumphboy]

Hi all
I have an intermittent issue with the keyless start on my CLS55. I have had it looked at by a Mercedes specialist who says there is no fault showing up on the Star diagnostics.
The symptoms are, that if the car is left for a while, say overnight, the keyless start (and stop) will usually work (even a number of times in a row) - before you drive anywhere. However, once driven any distance, more often that not, you cannot then shut the engine off with the start(stop) button, you need to use the key in the ignition to stop the engine. From that point, occasionally it will start again with the keyless button, but most other times it won't and you need to use the key in the ignition.
I have put new batteries in the key, which didn't make any difference.
I'm at a bit of a loss as to what to do now. Does anyone have any suggestions as to what might be going on, or what else I can do to diagnose the fault please? Thank you

 

[Gbrowncls55]

Does it say anything in the instrument cluster.e.g. Key not recognised or similar

 

[eight]

I think there's keyless antennae/receiver units fitted front and back on our cars to get the doors to unlock, maybe more inside the car for the actual keyless go - specialist could maybe identify which is used for the ignition. You'd expect it to work better with the engine running and the car batteries being charged, not the other when stood.
Or it could be a wiring problem below your knob. Bit of chafing perhaps.
Intermittent stuff like this can be weird. Car is standard? No funny garage door openers or anything similar that could potentially cause interference?

 

[triumphboy]

Does it say anything in the instrument cluster.e.g. Key not recognised or similar

Only once did I get a cluster message saying "check key battery" or something similar. At the time I though "bingo" that must be the issue, but I put new batteries in and it made no difference. That's the only time I've had a cluster message in the 6 or so months I've had the car and this issue has been 'consistently inconsistent' that whole time.

 

[triumphboy]

I think there's keyless antennae/receiver units fitted front and back on our cars to get the doors to unlock, maybe more inside the car for the actual keyless go - specialist could maybe identify which is used for the ignition. You'd expect it to work better with the engine running and the car batteries being charged, not the other when stood.
Or it could be a wiring problem below your knob. Bit of chafing perhaps.
Intermittent stuff like this can be weird. Car is standard? No funny garage door openers or anything similar that could potentially cause interference?

I had seen searching online for answers that the wiring below the knob can be an issue. But in this case the symptoms (in my layman's view at least) don't seem to be consistent with that? Also, I presume this kind of fault would show up on Star diagnostics?
The car is totally standard and has nothing that I can imagine is causing interference.

 

[Riva811]

Is the car battery OEM?

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[Skd884]

Is the car battery OEM?

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Yes.

 

[triumphboy]

Is the car battery OEM?

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Ah interesting point! It's a Varta with a Mercedes logo on it, I presume it is OEM? Photo attached.

By co-incidence when I first started her up this morning I got this message on the cluster (first time I've had this): "Battery protection: Convenience function temporarily unavailable". After a few minutes driving, another message popped up saying something along the lines of "convenience function now operational".

I then checked the battery voltage and it's only showing 12.2v (14.2v with engine running). It's cold today but 12.2v is not enough is it? I don't know when the battery was last changed (I've had the car for 6 months), but I do know that the car was standing doing virtually no miles at all for a year or so before I bought it.

Should I change the battery? Thanks.

 

[Riva811]

I don't get that message but I get things not starting up properly like command stays stuck on the mb logo, my parktronic misbehaving etc. The cold weather isn't doing favours but I can't recommend you to go buy an oem battery, perhaps diagnose it first before you spend £200 on one.
Edit:that looks oem

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[triumphboy]

I don't get that message but I get things not starting up properly like command stays stuck on the mb logo, my parktronic misbehaving etc. The cold weather isn't doing favours but I can't recommend you to go buy an oem battery, perhaps diagnose it first before you spend £200 on one.
Edit:that looks oem

Thanks, I'll get the battery checked out

 

[triumphboy]

Can anyone please tell me if my car (CLS55) has an auxiliary battery, or just the one main one in the boot?

 

[perrysock]

There is one small under the hood

 

[triumphboy]

There is one small under the hood

Thank you very much. Would anyone be able to tell me what the OEM model or part number for the aux battery is please? Is it a Varta VFB-H8 by any chance?

 

[Riva811]

Thank you very much. Can anyone tell me what the OEM part number for the aux battery is please?

PM me your VIN

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[triumphboy]

PM me your VIN

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Pm sent, thank you!

 

[Riva811]

Pm sent, thank you!

A2115410001

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[triumphboy]

A2115410001

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Thanks again!

 

[AMGeed]

Your main battery should be reading 12.6V+ fully charged so a top up with the charger might help.
Get the battery tested under load. I just had mine done and at 4.5 yrs old it failed the CCA test and required a new battery.

The aux battery is under the pollen filter on the n/s rear engine bay. Just one 10mm plastic nut to undo and the pollen filter cover lifts off.
If its not been changed a new one is one the cards. They are around £80 for an OEM Fiamm brand battery.

 

[triumphboy]

Your main battery should be reading 12.6V+ fully charged so a top up with the charger might help.
Get the battery tested under load. I just had mine done and at 4.5 yrs old it failed the CCA test and required a new battery.
The aux battery is under the pollen filter on the n/s rear engine bay. Just one 10mm plastic nut to undo and the pollen filter cover lifts off.
If its not been changed a new one is one the cards. They are around £80 for an OEM Fiamm brand battery.

Thank you very much. I had the battery tested under load today and it is "borderline weak", so I'm going to replace it.

Now I'm a little confused about actually what to replace it with, considering I would like to go for an "OEM" replacement. Would this Varta fit the bill?

www.tayna.co.uk/car-batteries/varta/h3/

or should I go with an AGM battery:

www.tayna.co.uk/car-batteries/varta/g14/

Or something else? I don't mind shelling out for a more expensive battery, as long as there's a benefit...I'm hoping the replacement battery might sort my original issue of intermittent Keyless Go, but maybe that's wishful thinking!

 

[Major774]

Go ask your MB dealership... prices are not that bad.

I went MB a few years ago.

For your Keyless start issue, does your car start every time with no issue via the ignition barrel? If so, I am pointing at the gear selector module, there could be something internally wrong.