Immobilises after six hours

[Keith Walker]

Hi everyone, I hope someone can help.
I have an E Class SE 220d 2017. After locking the car, exactly 6 hours later it immobilises itself. The siren sounds for 15/20 seconds and the car shuts down. Even the clock stops. I have to use the mechanical key to get into the car , then put the fob into the designated area and push the start button. The car then starts and resets itself. I have also tried leaving the car unlocked, but again it will immobilise after 6 hours but no siren will sound.
I have replaced the car battery, checked for a parasitic draw and replaced the 2 bonnet sensors. I took it to my local dealership to have it diagnosed on the star machine and they told me that it needs a new siren. I explains that this was happening even if I left the car unlocked?But they said that it needs the siren needs replacing and that by leaving the car unlocked drains the battery, as things are sill running if the car is left unlocked. I explained to him that I have done a voltage check on the battery 15 minutes before it was due to Immobilise and the battery was not drained, but he said that it needs a new siren. So I purchased a new siren and connected it, not fitted just connected, just to see what would happen. Sure enough six hours later the new siren sounded and car immobilised. I’m £500 in so far and still not sorted out. Any help on this would be much appreciated.

 

[Blobcat]

Hello and welcome,

The battery inside the alarm siren will most likely have leaked, this takes out the circuit board and causes numerous issues. Replace the alarm siren and all should be well again. Plenty have done it themselves on here.

 

[EmilysDad]

Hello and welcome,

The battery inside the alarm siren will most likely have leaked, this takes out the circuit board and causes numerous issues. Replace the alarm siren and all should be well again. Plenty have done it themselves on here.

but Keith said ....
. So I purchased a new siren and connected it, not fitted just connected, just to see what would happen. Sure enough six hours later the new siren sounded and car immobilised. I’m £500 in so far and still not sorted out. Any help on this would be much appreciated.

 

[EmilysDad]

alarm & immobiliser are two different things aren't they ...

 

[malcolm E53 AMG]

Have you checked the auxiliary battery it may control the alarm/immobiliser as one of it’s many functions. I think it’s in the form of a capacitor nowadays on the newer models. If this is failing it would account for the regular time lapse of the alarm sounding

 

[alexanderfoti]

In xentry (your car is too new for star) the ATA will tell you the last reason for sounding. I suspect this will lead you to the answer, otherwise its a difficult one.

 

[Keith Walker]

Have you checked the auxiliary battery it may control the alarm/immobiliser as one of it’s many functions. I think it’s in the form of a capacitor nowadays on the newer models. If this is failing it would account for the regular time lapse of the alarm sounding

Thanks for the reply, it makes good sense what you are saying but I don’t think there is a secondary battery or power source on the later models. Please correct me if I’m wrong and tell me where it might be.
Thanks again.
Keith

 

[Keith Walker]

Hi, thanks for the reply, I took it to a Mercedes dealership, so I’m assuming that they used the latest diagnostic test on it. They did give me a copy of the reading and what I could make of the results, it just stated the time and date of the alarm siren sounding. No cause just the time and date

Thanks again Keith.

 

[Keith Walker]

alarm & immobiliser are two different things aren't they ...

Yes I believe they are, meaning what exactly?

 

[mattkh]

Have you checked the auxiliary battery ................ I think it’s in the form of a capacitor nowadays on the newer models.

I am aware of this technology being used in the lightweight jumpstart gadgets.
If it is now being used in modern cars, please enlighten me as much as possible. Thanks.

 

[malcolm E53 AMG]

Thanks for the reply, it makes good sense what you are saying but I don’t think there is a secondary battery or power source on the later models. Please correct me if I’m wrong and tell me where it might be.
Thanks again.
Keith

 

[EmilysDad]

Yes I believe they are, meaning what exactly?

you say the car is immobilised after 6 hours but it's the alarm that's being triggered after 6 hours. The immobiliser is in operation as soon as the key is removed.

 

[alexanderfoti]

Hi, thanks for the reply, I took it to a Mercedes dealership, so I’m assuming that they used the latest diagnostic test on it. They did give me a copy of the reading and what I could make of the results, it just stated the time and date of the alarm siren sounding. No cause just the time and date

Thanks again Keith.

Is the reading you have a code printout? There is a different section that gives you the cause.

 

[Keith Walker]

In xentry (your car is too new for star) the ATA will tell you the last reason for sounding. I suspect this will lead you to the answer, otherwise its a difficult one.

Thanks for the reply

Is the reading you have a code printout? There is a different section that gives you the cause.

No, they just gave me this copy of the time and date no code as I can remember. I’m away on holiday at the moment, so I can’t check, but I will as soon as I get back home. Thanks for reply.

 

[Keith Walker]

you say the car is immobilised after 6 hours but it's the alarm that's being triggered after 6 hours. The immobiliser is in operation as soon as the key is removed.

Ok thanks, within the 6 hour window, I can unlock and gain entry as you would normally with the key fob and lock it up again, but then the 6 hours starts again from that exact time that I have locked the car up. However once the 6 hours have gone this is when the car totally shuts down, the clock stops, I can’t gain entry with the key fob. I have to use the mechanical key to gain entry, nothing works in the car at all completely dead, no interior lights, no central locking nothing. I have to put fob in designated area then push th start button. The car then resets itself and starts normally.

 

[Keith Walker]

Hi everyone, I hope someone can help.
I have an E Class SE 220d 2017. After locking the car, exactly 6 hours later it immobilises itself. The siren sounds for 15/20 seconds and the car shuts down. Even the clock stops. I have to use the mechanical key to get into the car , then put the fob into the designated area and push the start button. The car then starts and resets itself. I have also tried leaving the car unlocked, but again it will immobilise after 6 hours but no siren will sound.
I have replaced the car battery, checked for a parasitic draw and replaced the 2 bonnet sensors. I took it to my local dealership to have it diagnosed on the star machine and they told me that it needs a new siren. I explains that this was happening even if I left the car unlocked?But they said that it needs the siren needs replacing and that by leaving the car unlocked drains the battery, as things are sill running if the car is left unlocked. I explained to him that I have done a voltage check on the battery 15 minutes before it was due to Immobilise and the battery was not drained, but he said that it needs a new siren. So I purchased a new siren and connected it, not fitted just connected, just to see what would happen. Sure enough six hours later the new siren sounded and car immobilised. I’m £500 in so far and still not sorted out. Any help on this would be much appreciated.

Can I just add that when I say the car immobilises, I mean that the car shuts down completely. I have to get in using the mechanical key. When I’m in the car nothing is working, no interior lights, no central locking no display or ambient lighting totally dead. Only when I place the fob into the designated area and push the start button it resets itself and starts normally.
I also forgot to mention, I can get in the car normally within the six hour window using the key fob, but as soon as I lock the car up again the 6 hour countdown will start again from the moment I have locked the car from this point.
Thanks again everyone for your time and input
Keith.

 

[Keith Walker]

Right, I Stan corrected. Is there any way of testing these , and can they malfunction even though the display has not shown any error messages?

 

[malcolm E53 AMG]

They usually display an error message ‘auxiliary battery malfunction’ but if the capacitor fails to earth after 6 hours it may trip the immobiliser/alarm. I’ve scanned the net for your fault and nothing comes up so this is my best guess. No idea of the cost of a new capacitor from MB but if it were my car it’s certainly an item I would replace to rule it out considering the likely costs incurred with MB diagnosing the problem

 

[Keith Walker]

They usually display an error message ‘auxiliary battery malfunction’ but if the capacitor fails to earth after 6 hours it may trip the immobiliser/alarm. I’ve scanned the net for your fault and nothing comes up so this is my best guess. No idea of the cost of a new capacitor from MB but if it were my car it’s certainly an item I would replace to rule it out considering the likely costs incurred with MB diagnosing the problem

Thanks Malcolm, I’ll get it changed and hopefully see what happens. Much appreciated.