Hello,

Bought a 2003 sl500. Car had a red battery message on the display. Previous owner said it needed to recharge the battery.

icarsoft message: b1293 hardware circuit code between EIS and CAN-signal implausible.

I have driven the car for about 2 months now fixing other issues and about 2 weeks ago the RED battery message turned into a WHITE service brake message.

icarsoft message: c2495 check wake-up procedure of control module a7/3n1 sbc control unit

At first I checked the the brake pads. They still have life in them.
Then I checked the brake pads sensors with Icarsoft and both front and rear show ok.
Checked brake fluid it was full.
I then realized that a bunch of items were having an issue as well:
Front driver low beam out
Front pass high beam out
glove compartment light was not on.

Icarsoft: cant connect to Front pass SAM unit.
Icarsoft: front pass SAM unit showed:
terminal 30 at 0v
terminal 61 off
terminal 15 - - -

I decided to pull the front and rear battery and test at autozone. They told me both are good.
volt meter showed:
Front :12.73
Rear: 12.51

when the car is on both go over 14v.

a few days later I decided to charge the rear battery with cheap charger from Amazon.
Charged to 13v installed back in car and BOOM the front passenger SAM had power. All the symptoms disappeared except:
b1293 and
WHITE brake service display message went back to red battery message.
So I though this was good, I had some progress.


But in a few hours when I started the car again I was back to no front SAM communication with all the symptoms and again White brake service message.


I decided to test the rear battery further.
I charged it to 13v in the afternoon
left it to rest over night
Morning resting voltage was 12.87
which I believe is good.

Installed back in the car and with 12.87v started the car but still NO communication with front SAM.
white message for brake service
glove box light not working
front left low beam out.

So fresh off the charger I get the SAM to function.
but at 12.87v the SAM will not function.

next I’m thinking to track down if the pre-fuse box under the glove box is getting power.


Any Ideas?

 

I have a 05 SL500 and these cars are super sensitive to voltage. The best thing to do is make sure your battery terminals are tight and keep it on a trickle charger every time it's in the garage.

I know it sounds crazy but I've seen tons of dash messages , accessory failures all go away with a fully charged consumer battery.

 

If yours is not a daily driver, I would recommend buying a good self regulating charger and keep it connected to the consumer battery when in not in use. It will keep your starter battery charged too. That has been my successful routine Best of luck

 

Front SAMS are known to have corrosion issues on the connectors, so that would be a good place to start. Also check the CAN hubs, especially the one in the passenger footwell. They can also have corrosion issues.

 

Thanks for everyone’s input, its my daily driver I do about 20 miles each day to work and back.

I’ll check on the CAM connection on my days off. I did see a little bit of dried water spots on top of the passenger fuse box, but it is a 19 year old car and I guess thats to be expected. I’ll have to check for corrosion at the front SAM.

Im not sure if its a corrosive problem. Like I said if it gets a fresh charged consumer battery = 13v front SAM is active.
but at 12.87 it will not work. Crazy how only .13v effect the car.

If anyone has a driver side low beam go out, check for other issues such as glove compartment light not working. If its multiple issues than don’t bother spending money on front low beam. Look at the passenger side SAM.
Hopefully I can find the problem and report back with a solution.

 

As others have said these cars need good batteries, I don't mean good and charged, I mean decent brands that can provide the CCA and hold current. Its not enough to just assume that if the voltage is at 13V all is good. I would avoid buying trickle chargers personally, I have never had any issues once I bought a genuine Mercedes battery, I can leave it in the dead of winter for a month and it will start right up, no low voltage 'convenience function not available' messages on dash etc. I work away and often leave my car many weeks never had issues starting her once I got the Mercedes battery. I had previously bought brand new alternative brands and within 2 weeks I started getting low battery warnings.

I would suggest you ditch the rear large battery and buy the genuine Mercedes one.
Second, as for the brake error message, I have had this and you cannot clear it ! the cars brake system has a safety feature that does not like anyone working on the brakes, pads callipers etc, unless you have told the car first. If you work on any area of the brakes, you can use tell the car by using your iCarsoft, there is a menu option in the service page. If however you have not done this, you will need to take it to a garage and get them to use their Star on it. I had to do this and also get my software on the car all updated before they could clear the brake error message.

Good luck !