I have a (2008)GL 450 that we picked up days ago, but i didn't check on anything before we replaced the battery. After replacing the battery 2 noticed 2 issues.
1. the radio is not working. I cannot turn the knob for volume as it doesn't not work, and i cannot press the buttons on the steering.
2. The phone/blue tooth device does not work. When i insert it into the Slot. It does not flash blue. No lights turn on. The "Tel" option states "not available" and i have no idea what i could possibly do about that.
Additionally, the car states that the break light is malfunctioning, but that isn't the case as we have tested it. We assume this occured after replacing the battery, we even unpluged the aux battery to replace that one as it is old, but came back empty handed on our search.

 

Welcome! Please post a photo of the GL. Try posting the question in the X164 section where owners will see it and make suggestions.

 

moved to X164 forum...

 

Did you disconnect both batteries at the same time? If yes, that's the issue. You may need STAR to reinitiate the modules.

 

Yes we did disconnect both of them. What is STAR?

 

The proprietary diagnostic system Mercedes uses for your GL.

 

After replacing battery, did you check all circuit breakers?

 

No?

 

will I have to take it an Mercedes dealer for that?
The car is rather old I don’t even know if it has warranty on it.

 

not really, there are independent shops that have this system, they either licensed it from MBUSA or have it from another way. Don't pay dealership rates.

 

ok. Any trip to the dealer for this problem is going to be 2 to 300 bucks plus.
check all circuit breakers first.

 

I'm sorry its about 2 months late but where can I find these circuit breakers?

 

If I recalled correctly, there is one under the hood for the GL and under the floor cover near the tailgate, hopefully someone has the actual diagram showing the locations of them.

 

Sorry to hijack the thread.

Will this be the same scenario with a w164? I know w164 is a different beast to the x164. I just replaced the auxiliary batteries on my w164 and did not notice any problems. Both batteries disconnected simultaneously.

 

for my 2007 GL450 (115k miles), I've replaced the two batteries all together two rounds.
in both cases, there is a brief moment that both batteries are removed from the SUV.
did not cause any problem

 

No problems here either. IIRC, you have to remove the main battery to replace the Aux battery, so it is unavoidable. There aren't circuit breakers for the stereo, just fuses. Fuse chart

 

Mate! That electrical fuse map is gold! Useful information for diagnostic