4happiness

After researching the issue of my 08 r320 locked in park with a warning light telling me to go directly to the dealer for service, I concluded that the intelligent servo module must have become defective. Before I could have it towed to a shop, I decided to install a new battery. While I had the front passenger seat removed, it seemed proper to change the little auxiliary battery which is located under the carpet a little forward from the main battery. I did catch a comment earlier this morning that the auxiliary battery's sole function is to allow the transmission to go out of park.

I upgraded the $150 mb oem auxiliary lead-acid battery to a $20 agm "ub1213 " from batteries and bulbs.

Somehow, this did the trick and it's back on the road.

So, I guess that this over-engineered system may have an easy fix after all. Makes me wonder how many people have been hit with a $1,300 or more repair bill from their friendly mb dealership to r and r the ism when all that was needed was a little battery replacement.

efzauner

great news and info.. Id your ub1213 fit exactly? Where the terminals the right size? On my 2011 R350 the OEM aux battery has a 0.25 and 0.187 terminal. The replacement battery had both at 0.25inch.

thanks