SLK55 eco not working!

Page may contain affiliate links. Please see terms for details.

Oscar 473

Active Member
Joined
Dec 24, 2016
Messages
120
Location
South East
Car
C63 ppp estate
Hello

my wife is having a problem with her car and I’m hoping that someone on here can give some suggestions about what the problem might be.

The car is a 12 plate SLK55. The car is refusing to use the Eco function. The symbol on the dash disappears and the car does not drop onto 4 cylinders. This is intermittent at the moment and no engine warning light is displayed. I have charged the battery with my Ctek charger. The charger shows that the battery is partially charged but the charger will no go into it’s maintenance mode which makes me wonder about the battery. The car still has it’s original battery. The battery starts the car OK, so it’s obviously not that low, but does anyone know if the Eco mode is very battery sensitive? Typically the car will start and run for a few miles with the Eco and stop / start functions working fine, then it will drop out.

As I have said, I’m hoping that the knowledgeable folks on here migh have some suggestions about what is happening.

thanks very much.
 
It’s of an age where changing the battery is almost a no-brainier

I think that is the source of your problem
 
I suspect you are right. It would be an easy fix as well, but I’m wondering if anything else springs to mind?

silly question time, where is the battery on an SLK ? If it is changed does the car require any reprogramming like some BMWs?

Thanks again.

p.s. When this happened I thought it would be interesting to see how the mpg would change. My wife was very smug in telling me that the car was still getting over 30mpg! My C63 wouldn’t get that if it fell off a cliff!
 
Not 100% sure of the set up on a SLK55 but many of the Eco equipped cars have an Auxiliary Battery. This is called in to action to power various consumers when the Eco system has activated and presumably in your SLK55 when cylinder deactivation is operational. On E classes at least these Auxiliary batteries are notoriously fault prone and require replacement, but if so you should get an error message to this effect. It is possible that in your case that rather than it having a fault it is no longer holding a charge sufficient to allow the Eco system to operate. I believe that charging the main battery will not charge the auxiliary battery. I would look to see if the SLK 55 has an auxiliary battery and either try charging it with the CTEK or maybe just save the hassle and replace it. I had one go on my E class under warranty and recall the dealer indicating it was not an expensive part and it only took about 1 cup of coffee and a read of the paper to get the job done.
 
Have you had it plugged in?
 
As in, plugged into a Mercedes diagnostic machine? No. It’s due a service in the foreseeable future but that will probable be postpone.
 
As in, plugged into a Mercedes diagnostic machine? No. It’s due a service in the foreseeable future but that will probable be postpone.
Yes. I would get that done first just in case anything comes up.
 
Agree that your battery is passed it's prime, and I would definitely be changing it.
The SLK of all generations has always been dependant on an excellent battery to perform properly.
You can find the battery position and other info here
Battery replacement 172
from the dedicated SLK forum

I would seriously consider joining the forum too, they have a great wealth of knowledge :)
 
Thanks very much for this, I’ll definitely look into joining this forum.

Does the 5.5 let SLK have an auxiliary battery?

Also, is there a prefered make of battery manufacturer? Lucas used to do decent ones but it is many years since I’ve bought a car battery!

Thanks again.
 
As JimmyR has pointed out above, the R172 with ECO does have an auxiliary battery.
This taken from the SLK site mentioned,

"Yes, on mine there is one under the hood (passenger side) and one (a motorcycle battery) in the cabin behind the drivers seat at floor level in the bulkhead behind a piece of carpet that covers the entire bulkhead. I have ECO which is dependent on that little fella but I don't know if ECO is standard. If you have the little one, that's where it will be.

Access is gained by moving the seat as far forward as possible, leaning in and lifting the carpet on the bulkhead to access it. It's a bitch to access though"

One of the Mods on there has a R172 55, so I should imagine any questions you have would be answered pretty quickly
 
Just a quick update on this.

The car has been in for service and, not surprising, the original auxiliary battery fitted to the was no good. This was changed, but there are still problems with the ECO not working as it should.

When it gets sorted I’ll post another update in case someone else can benefit.
 
Just a quick update on this.

The car has been in for service and, not surprising, the original auxiliary battery fitted to the was no good. This was changed, but there are still problems with the ECO not working as it should.

When it gets sorted I’ll post another update in case someone else can benefit.

By the sound of it, the main battery will need changing as well.

There are other reasons why the Stop/Start won't work properly, but 9 out of 10 it's one of the two batteries, or both.
 
  • Like
Reactions: LTD
In the mean time don't let Gerbil Tongueboil find out that your 5.4 V8 has a faulty Eco system, she wouldn't be able to sleep at night, even with the landing light left on . :thumb:
 
I would be worried if the Eco light didn't work on my car, only because I like everything to be working properly :rolleyes:
 
I would be worried if the Eco light didn't work on my car, only because I like everything to be working properly :rolleyes:
Same here! It's OK for me to switch off the darn thing when I decide to (which is all the time), but God forbid that there will be something broken in car - I won't be able to sleep at night....

Besides, it's a handy way to check the condition of the battery.... :D
 

Users who are viewing this thread

Back
Top Bottom