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BAS/ESP Light Only On.....Question.

2K views 5 replies 3 participants last post by  43sqd 
#1 ·
My ML is unfortunately making a trip to my indy tomorrow because i dont have a professional grade scanner. Ive read the threads regarding this light coming on and with some pretty scary results (i.e. brakes locking up). But i have a few questions.

Mainly, does this light have to be on for the code(s) to be accessible, or will there be residual codes stored deep in the ETC which he will see?
I ask only because i want to know if he will have to drive the vehicle, have the light come on, and hook up the scanner while its running or not.

Secondly, just a curiosity question. The manual states with this light on the BAS(Brake Assist System) and the ESP (Electronic Stability Program) will be turned off. Why does the little triangle in the speedometer not come on if the light turns off the ESP? On the same thought, why does the ESP toggle switch not do anything?

And i guess finally, what does the BAS system actually do. How can anything ASSIST an ABS system. It gives some shitty explanation in the manual, but what is actually happening? What parts are actually working to aid the ABS?


Any light to these questions would be appreciated guys and gals. Thanks
 
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#2 ·
Oeschej, this really shouldn't be the time that you break out the learning curve requests. As you already know there is a problem somewhere and the only way to find out what is to have the codes read.

Although it would be ideal if everyone had a professional grade scanner or an SDS scanner, but that would be impossible. The alternative is to find an independent mechanic who has one who can read the codes ('C' codes) from the ESP/Traction Control Module, not the ETC.

A great majority of forum members do all their own repairs, which is all well and good. But when it comes time that they need a mechanic to read codes or perform a repair that they can't accomplish, they don't know who to go to. Everyone should find an independent mechanic that has a professional grade scanner or else you will always be at the mercy of the dealer.

You are panicking because you have a light on the dash. But you will always have brakes; only that feature/s will not be functional. The ESP-ETS-BAS, etc. is an extremely convoluted system and requires an engineering degree to fully understand.

Below is some info. on how these systems work. If you want to go to M/B and get fleeced, then that's your decision.
 

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#3 ·
Lol. I appreciate the feedback 43sqd. Was just wondering out of curiosity. I know very well that when that light is on, the codes need to be read to determine the right plan of action. Thank you for clarifying that it will be a C code from the ESP system.

Since i have no ambition to go get an engineering degree any time soon, i will conclude that these sytems are over my head, there is a fault somewhere, and hopefully the indy will find a stored code is the ESP module.

Thanks for the info
 
#4 ·
Update:
Got the truck back from my Indy. Found no codes at all. So im assuming you will only see a code if the light is on, which i would have to get a scanner on it before its shut down again.
Or, his scanner wasnt good enough (Snap On though....?) and this is a Star only type of code read.

Either way, im going to grab another brake light switch from the dealer, and hope for the best. Otherwise i dont know......
 
#6 ·
Before you do anything else, you have to determine if your indy has a professional grade scanner and if he accessed the Traction Control Module. If he only read the ECM no codes will be stored there, it has to come from the ESP/Traction Control Module.
 
#5 ·
I have a 2000 ML430 all 3 of my lights come on daily. It has been to the Mercedes shop a few times. The last time they kept it a week to check the codes and everytime the lights came on there were no codes. Any thoughts on that. My service man said not to worry about it since they can't get a code and the worst thing that would happen is that it would go into limp mode. Is this a normal thing with the MLs?
 
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