Hold function lost

[merc07]

Did I mention start stop or something ?
I have had the car since 2015 with 15k on the clock - it now has 115k, start stop has never worked, 75% of the time the car didn't even know it had it - now it's 100% disappeared.

However the original issue here was the Hold function stopped working after a brake fluid change, the error relating to a battery sensor / rear sam communication fault.

This morning I unplugged the sensor, left it off for 5mins for good measure and plugged it back in - hey presto, the hold function is back and the error went to a historic which I was able to delete.

It made no difference to the stop start function but nevermind

Fingers crossed....

 

[Tonygw]

Im convinced the start stop system is what caused the timing chain to wear out early on my C250 cdi. Others seem to last a lot longer when doing motor way miles. Its a common thing.

Incidentally modern cars DO NOT HAVE up-rated mechanical components to deal with start stop, its only a software modification. They are simply tested to see if they can withstand the strain. In fact they are often VA-VE engineered to reduce costs. The "only" additional component to take some strain off the battery are the installation of super capacitors to provide short term power to the "normal" starter motor.

Everything else is the same. 3 years will not show up any issues. But 5-10 years will and does. Not just Mercs
Audi timing chains are a joke, They fail by the hour.

But that aside, start stop is very annoying.. one of the worst inventions

 

[sgregory124]

Incidentally modern cars DO NOT HAVE up-rated mechanical components to deal with start stop, its only a software modification.

I think Denso and the majority of car manufacturers would disagree with you there?

That snippet is from this article:

Auto-Start/Stop: Is It Bad For My Engine? (Mythbusting)

Back in 2012, the Obama Administration finalized the standards of automotive companies to encourage a corporate fuel economy average of 54.5 miles per gallon

mechanicbase.com

 

[Gazwould]

Does early Stop Strain 2011 - 2015 Mercs actually have any of this ?

I much prefer and respect the real world experience on Stop Strain of multiple Mercedes independents .

 

[OldskoolRS]

Did I mention start stop or something ?
I have had the car since 2015 with 15k on the clock - it now has 115k, start stop has never worked, 75% of the time the car didn't even know it had it - now it's 100% disappeared.

However the original issue here was the Hold function stopped working after a brake fluid change, the error relating to a battery sensor / rear sam communication fault.

This morning I unplugged the sensor, left it off for 5mins for good measure and plugged it back in - hey presto, the hold function is back and the error went to a historic which I was able to delete.

It made no difference to the stop start function but nevermind

Fingers crossed....

Sorry, my sincere apologies as it was me that led to the ongoing discussion. Glad to hear that you got the hold function issue sorted out. Fingers crossed that's the end of it (both the fault and the arguing ).

 

[merc07]

Sorry, my sincere apologies as it was me that led to the ongoing discussion. Glad to hear that you got the hold function issue sorted out. Fingers crossed that's the end of it (both the fault and the arguing ).

That's ok, I was joking, when ever it gets mentioned, the thread goes mad, same as electric Vs diesel threads !
The hold function is holding up still

 

[Allybassman]

W204 C350

The hold function, not the auto hold on a hill, but when you press the pedal again seems to have disappeared altogether?
I noticed it right after the car was in for a brake fluid change although to be honest I can't be 100% sure it hadn't already failed and I do realize.
My ECO mode also completely disappeared at the same time - that's how I noticed something was up.

I have one current error on the rear Sam, 'communication with the battery sensor has a malfunction'

Any ideas ?

Hi - did you every get this sorted?

I have the exact same issues.... I replaced both the main and aux battery as they were the original 10 year old ones.

I've got the following code

U113E00 - Communication with the battery sensor has a malfunction.

I'm thinking of replacing the battery voltage sensor that sits on the negative terminal of the main battery....

Cheers

 

[merc07]

Hi - did you every get this sorted?

I have the exact same issues.... I replaced both the main and aux battery as they were the original 10 year old ones.

I've got the following code

U113E00 - Communication with the battery sensor has a malfunction.

I'm thinking of replacing the battery voltage sensor that sits on the negative terminal of the main battery....

Cheers

Yes, all I did was disconnect and reconnect the sensor from negative terminal..

 

[snotrag]

Bumping this - been perplexed as to why my new S204 C350 Cdi doesnt seem to have functioning Brake Hold like my E Class did (Hill assist works fine, this is seperate). I was initially a bit annoyed and guessed this might be one of the 'premium' features of the larger and more expensive E Class that the C doesnt have, I was prepared for their to be somethinf I'd miss!

It does however seem from the manuals etc that all facelift W204 C's should have it.

No codes, or errors, (ABS or wheel speed sensor would be an obvious one) but I'll try the battery trick and report back

 

[merc07]

Bumping this - been perplexed as to why my new S204 C350 Cdi doesnt seem to have functioning Brake Hold like my E Class did (Hill assist works fine, this is seperate). I was initially a bit annoyed and guessed this might be one of the 'premium' features of the larger and more expensive E Class that the C doesnt have, I was prepared for their to be somethinf I'd miss!

It does however seem from the manuals etc that all facelift W204 C's should have it.

No codes, or errors, (ABS or wheel speed sensor would be an obvious one) but I'll try the battery trick and report back

Did you try the above, mine has been working fine since I did it....

 

[markjay]

Bumping this - been perplexed as to why my new S204 C350 Cdi doesnt seem to have functioning Brake Hold like my E Class did (Hill assist works fine, this is seperate). I was initially a bit annoyed and guessed this might be one of the 'premium' features of the larger and more expensive E Class that the C doesnt have, I was prepared for their to be somethinf I'd miss!

It does however seem from the manuals etc that all facelift W204 C's should have it.

No codes, or errors, (ABS or wheel speed sensor would be an obvious one) but I'll try the battery trick and report back

The HOLD function is part of the Start/Stop system - is the system working fine? Do you have the green ECO light in the instrument cluster? If the ECO light in the instrument cluster (not the one on the button on the lower switch panel) is amber most of the time, then one of the two batteries (starter and auxiliary) might be weak.

 

[merc07]

Could be an indication if they are related but my start stop has never worked from new, I don't have a green or an amber light 99% of the time but the HOLD function works just fine...

 

[Gazwould]

Showing with this model SS and brake HOLD are not linked and thus I have my auxiliary battery removed to permanently disable SS and brake HOLD works !

 

[Allybassman]

Just to report back - I've changed both batteries and the voltage sensor on the battery and still no hold or stop/start feature working.

I don't use SS so not bothered about that, but the HOLD feature i do miss!

Two codes are brought up still - Must be something to do with the rear SAM.

Rear SAM - Rear signal acquisition and actuation module

Fault code: B21DE71 B21DE71 - The relay 'Additional battery' has a malfunction. The actuator is blocked.

Fault code: U113E00 U113E00 - Communication with the battery sensor has a malfunction. - Changed the sensor but the code came straight back.

 

[snotrag]

In my case - got the thermostat changes (1 hour, instant 10mpg improvement, why oh why do people not do this, suspect it might be why it was traded in!).

However that did not fix the availability of ECO - still shows in yellow, so not ready. Tested both battery voltage, Aux is 13.6, appears recent. Main batter showing only 12.3V, which is low - no problems starting or otherwise but it looks original and potentially a bit weak. Could do with reading the Merc specific codes now before throwing a battery at it (nothing on OBD2) but again, suspect whatever is not allowing the ECO/Start-Stop function to reach its ready mode is also preventing it from doing the brake hold (will need good power for the abs modulator pump presumably before it trusts itself to hold).

 

[Allybassman]

In my case - got the thermostat changes (1 hour, instant 10mpg improvement, why oh why do people not do this, suspect it might be why it was traded in!).

However that did not fix the availability of ECO - still shows in yellow, so not ready. Tested both battery voltage, Aux is 13.6, appears recent. Main batter showing only 12.3V, which is low - no problems starting or otherwise but it looks original and potentially a bit weak. Could do with reading the Merc specific codes now before throwing a battery at it (nothing on OBD2) but again, suspect whatever is not allowing the ECO/Start-Stop function to reach its ready mode is also preventing it from doing the brake hold (will need good power for the abs modulator pump presumably before it trusts itself to hold).

Funny you should say Thermostat... my car never gets up to 90 (indicated on the gauge) always hovering around 80 or lower. Got a new one to throw in when I have some time.

 

[merc07]

In my case - got the thermostat changes (1 hour, instant 10mpg improvement, why oh why do people not do this, suspect it might be why it was traded in!).

However that did not fix the availability of ECO - still shows in yellow, so not ready. Tested both battery voltage, Aux is 13.6, appears recent. Main batter showing only 12.3V, which is low - no problems starting or otherwise but it looks original and potentially a bit weak. Could do with reading the Merc specific codes now before throwing a battery at it (nothing on OBD2) but again, suspect whatever is not allowing the ECO/Start-Stop function to reach its ready mode is also preventing it from doing the brake hold (will need good power for the abs modulator pump presumably before it trusts itself to hold).

If you pootle around (not saying you do) it may never change to green - if you floor it in a non eco friendly way, the green eco light will more likely come on - at least that's what I've seen in the 5% of the time I even have a light.

But now if mine does work and turn green, I switch it off anyhow !

 

[Noitz]

I'd like to revive this thread as I've had an anomaly with the brake hold on my 2015 SLK250. I've not used the car for 20 days due to the missus being ill, but today we decided to go for a short run only to find the Hold function didn't work. We drove approx 21 miles on A and B roads before stopping for about 20 mins to feed some ducks by a lake, got back in the car and then drove another 5 miles to a cafe without the Hold function operating at all. After our coffee break we drove back home as the missus was getting very tired and the Hold function was working again. Could this this anomaly be due to low battery voltage as the car had been standing too long, or is there something else I should be looking at. Incidentally, the Stop/Start function hasn't worked since I bough the car last year.

 

[Tonygw]

Almost certainly it's due to a battery at the end of its life. A new battery will sort it. Did on mine with exact same symptoms.

 

[Noitz]

Thanks Tony, I half suspected it may be time to replace both batteries.