Brake Hold Function Stopped Working

[bertg]

Afternoon, can anyone help? my much loved 2013 B Class W246 petrol isn't playing nicely. I've recently noticed that the Brake Hold function has stopped working and i do have a steep hill near where i live to test it. Any ideas where i start looking. BTW car was recently serviced & Mot so i believe the pads are in good condition.

 

[malcolm E53 AMG]

Have you checked the state of the battery the car ECU will start to shutdown non essential services if it’s under voltage it should be 12.6V or thereabouts to be healthy

 

[w204benz]

As above - check the battery.

I had the same problem recently - battery was on it's last legs and if the voltage dropped a bit too much when cranking, the module would throw an error and disable Brake Hold until I cleared it. Wouldn't happen if the battery was fresh off the charger and could keep the voltage high enough.

I put a new battery in it and Brake Hold works great now.

 

[bertg]

Have you checked the state of the battery the car ECU will start to shutdown non essential services if it’s under voltage it should be 12.6V or thereabouts to be healthy

i'll check it tomorrow, thank you.

 

[bertg]

As above - check the battery.

I had the same problem recently - battery was on it's last legs and if the voltage dropped a bit too much when cranking, the module would throw an error and disable Brake Hold until I cleared it. Wouldn't happen if the battery was fresh off the charger and could keep the voltage high enough.

I put a new battery in it and Brake Hold works great now.

to be fair it is 10 years old. my concern is that i recently had it serviced. i don't believe in coinsidences.

 

[malcolm E53 AMG]

to be fair it is 10 years old. my concern is that i recently had it serviced. i don't believe in coinsidences.

If the battery is 10 years old it’s done well on average my car batteries last circa 7 years after which I look out for tell tale signs like the one you’re experiencing that it needs replacing

 

[w204benz]

to be fair it is 10 years old. my concern is that i recently had it serviced. i don't believe in coinsidences.

Mine was just over 11 years old, so I guess yours is probably at the end of its life too.

I'm not familiar with the W246, but if you can get the service menu on the instrument cluster to show the voltage, check it after the car has been sitting overnight. If it's below 12V, I'm 99% certain a new battery will sort it out.

I've heard that low voltages on these newer cars can cause all sorts of issues, so I considered losing Brake Hold as a friendly hint before anything more serious fails!

 

[bertg]

thanks everyone for this, 1 more silly question, if it is the battery, do i need to go to merc or can i get a replacement elsewhere? i will of course stick to a branded product whatever brand of battery i have.

 

[AndySlade]

thanks everyone for this, 1 more silly question, if it is the battery, do i need to go to merc or can i get a replacement elsewhere? i will of course stick to a branded product whatever brand of battery i have.

Can you confidently change it yourself? If so consider Tayna Batteries or M-B Grangemouth dealership which supports this forum.

 

[malcolm E53 AMG]

Plenty of tutorials on YouTube regarding changing a battery. Just remember negative terminal removed first then positive and reverse to connect so that the negative is the last to connect.

 

[bertg]

Can you confidently change it yourself? If so consider Tayna Batteries or M-B Grangemouth dealership which supports this forum.

if the battery needs replacing i think i will give it a try, i'll feedback with my test result.

 

[bertg]

Have you checked the state of the battery the car ECU will start to shutdown non essential services if it’s under voltage it should be 12.6V or thereabouts to be healthy

Well, the results are in, just put my meter across the terminals from cold and it measured 12.15V. Started the engine and measured again and it went up to 14.99V. See pics. So, based upon everyone's experience i need to replace my battery?

 

[DSK]

Yes. My local MB Indy advised a new battery as mine was showing 12.2v despite the always starting, driving and well, when he started investigating my intermittent non strut issue.

As above it should be showing roughly 12.6v.


Sent from my iPhone using Tapatalk

 

[w204benz]

It looks like a new battery would be a good idea. To be fair, mine would also start and drive without any problems, even at 12V. Until the weather cooled down a bit, and the lack of battery capacity quickly became apparent.

I had suggested checking through the instrument cluster as it puts a bit of a load on the battery, although I suppose with the ignition on and engine off you'd get the same results with the meter.
If you tried that on a cold engine, I suspect the voltage would quickly drop below 12V.

As above, the new battery is stable at around 12.6V even under load.

 

[bertg]

It looks like a new battery would be a good idea. To be fair, mine would also start and drive without any problems, even at 12V. Until the weather cooled down a bit, and the lack of battery capacity quickly became apparent.

I had suggested checking through the instrument cluster as it puts a bit of a load on the battery, although I suppose with the ignition on and engine off you'd get the same results with the meter.
If you tried that on a cold engine, I suspect the voltage would quickly drop below 12V.

As above, the new battery is stable at around 12.6V even under load.

when it was cold it measured 12.15V and then when i started it up it changed to 14.99 so that immediately suggested that the alternator was doing it's thing. As mentioned above, i suspect non essential services stop working when the battery voltage drops.

Mine was just over 11 years old, so I guess yours is probably at the end of its life too.

I'm not familiar with the W246, but if you can get the service menu on the instrument cluster to show the voltage, check it after the car has been sitting overnight. If it's below 12V, I'm 99% certain a new battery will sort it out.

I've heard that low voltages on these newer cars can cause all sorts of issues, so I considered losing Brake Hold as a friendly hint before anything more serious fails!

1 more on this thread so please don't shoot me down, it's suggested that when the battery voltage drops the ECU shuts down non essential services. So, when i start the car and it's running with a battery voltage of 14.99 Volts, why doesn't the brake hold function kick back in again? What else could cause it to stop working?

 

[dry run]

My guess would be that when you first turn on the ignition the weak battery voltage is detected and systems disabled. It probably stays like that until it is started again with sufficient charge in the battery. If your starting charge value is always low, it will detect that and disable regardless of what the running voltage is. But I'm no expert

 

[w204benz]

1 more on this thread so please don't shoot me down, it's suggested that when the battery voltage drops the ECU shuts down non essential services. So, when i start the car and it's running with a battery voltage of 14.99 Volts, why doesn't the brake hold function kick back in again? What else could cause it to stop working?

I did a few experiments before I changed my battery. What I observed is that when the module sets a "voltage error", it doesn't automatically clear once the voltage rises again. It doesn't matter if you use an external charger to top off the battery before starting the engine or let the alternator charge it while the engine is running.
Brake Hold (and perhaps other functions) will remain disabled while the error code remains set.

Clearing the error re-enables all functions, but I vaguely remember an ignition cycle count - after a number of consecutive ignition cycles where the voltage doesn't drop too low (might have been 8 or 10), the error would automatically clear.

So if you change the battery and don't have a tool to clear the codes, you will still get Brake Hold back - eventually.

 

[bertg]

My guess would be that when you first turn on the ignition the weak battery voltage is detected and systems disabled. It probably stays like that until it is started again with sufficient charge in the battery. If your starting charge value is always low, it will detect that and disable regardless of what the running voltage is. But I'm no expert

makes perfect sense, thank you.

 

[bertg]

I did a few experiments before I changed my battery. What I observed is that when the module sets a "voltage error", it doesn't automatically clear once the voltage rises again. It doesn't matter if you use an external charger to top off the battery before starting the engine or let the alternator charge it while the engine is running.
Brake Hold (and perhaps other functions) will remain disabled while the error code remains set.

Clearing the error re-enables all functions, but I vaguely remember an ignition cycle count - after a number of consecutive ignition cycles where the voltage doesn't drop too low (might have been 8 or 10), the error would automatically clear.

So if you change the battery and don't have a tool to clear the codes, you will still get Brake Hold back - eventually.

once again thank you for all your help, someone from this forum advised me to purchase a diagnostic device called icar soft and it has worked well in diagnosing another problem i also have so, i'll hook it up and see what it comes up with. But i think based upon everyone's advice, i will get a new battery, the evidence is clear, 12.1V is too low.

 

[Blobcat]

once again thank you for all your help, someone from this forum advised me to purchase a diagnostic device called icar soft and it has worked well in diagnosing another problem i also have so, i'll hook it up and see what it comes up with. But i think based upon everyone's advice, i will get a new battery, the evidence is clear, 12.1V is too low.

>12.4 at rest, engine off is required