DrSmart

Does anyone know how to unlock the automatic transmission, from park to neutral, when we run out of battery?

Thanks!

rapidoxidation

I'd love for someone to show me I'm wrong, but IIRC it can't be done. That's what wheel dollys are for.

Max Blast

That's what the aux battery is for. It has one job, and that is to allow the ISM to shift out of park when the main battery is drained.
Replace it, and you will be enabled to shift to neutral.
Btw, in order to get at it you have to remove the main battery at which point you might as well replace that as well.

DennisG01

Hook up a jump pack? Or cables from another car? Other than that, I'm out of ideas

DrSmart

My car doesn't give any signal, and it's not the battery. So I need to shift to neutral to push the car!

eric_in_sd

How do you know it's not the battery?

DrSmart

Change it with another one and car keeps the same!

DennisG01

If you're 100% positive the battery (or connections) aren't the problem, then the only other thing I can think of (besides wheel dollies as noted above) would be to unbolt the driveshafts.

eric_in_sd

Since you are sure the battery is fine: I was going to ask if you had queried the ISM and TCM with your scan tool, but "doesn't give any signal" probably means the electronics are fried and it's a parts vehicle.

Unbolt the driveshafts, or put it up on dollies, and wheel it to your disassembly area. There is no way to shift out of Park without control over the electronics.

Good luck.

Max Blast

If ISM Fried, car is now parts.

Max Blast

.

eric_in_sd

ISMs are on Ebay for $300. Have to program it, of course. I know we go around saying this makes it a parts car; is that because whatever fried the ISM probably fried a bunch of other stuff too? Like water damage?

Or is that assuming the dealership rates for replacing the ISM?

DrSmart

Looks like an electrical fault, and not ism problem. I already check booth sam from back and front sam and they are correctly working too.

eric_in_sd

The ISM is an electromechanical module. The S stands for servo. Whatever it does mechanically can be duplicated with the module removed.

BlackML550

There was a fellow in the W251 fourm that parked his car in a very tight garage that when the battery went flat he couldnt get into change it or even jack it up to move it. Jumping it didnt work and sounded genuinly stuck. You could see how angry he was getting with each post as no matter what people suggested, he'd snookered himself. I told him the only way was to spill oil under each wheel and slide it out. I reckon this was the only way out. Never heard from him again.

eric_in_sd

What a mess. Even if you oiled the garage floor, the vehicle would likely slide sideways coming out, scraping the walls.

DrSmart

I already resolve my problem, that is a eletric issue (near sam under front seat). But there are something that makes consumes battery yet.
This car its very rare in my country (Portugal) and very dificult to get some parts, even in Mercedes official dealer.
I will keep in touch some news from my GL.
Thanks to all friends from Mercedes forum!

Max Blast

Sorry, did we ask you this already; does the battery compartment appear to have had water in it?

DrSmart

No problem. Yes. Have.

Max Blast

Well, then jack it up on sliding Dollies to move it around to where you can work on it - starting with removing and inspecting all electrical modules under each seat. They are very likely damaged from sitting in water at some point and you likely have more problems than a fried ISM.