Hey all, over the weekend, I was driving our GL350 to the store, put in in park left it run while my wife ran into the store and when we went to leave, it wouldn't engage into reverse or neutral when I pushed the brake and flicked the shifter up like normal. I tried shutting it off and restarting which did not work either. Has anyone experienced this? It will still go into drive and if I push the end of the shifter back into park, but we have not been able to get it into reverse since Friday night.

I've tried researching and some of the articles I've found say it could be a dying auxiliary battery or a transmission intelligent servo (ISM) that may need to be replaced. Would it be possible the shifter assembly with the cruise lever is bad?

We don't have a dealer very close (45 miles away is the closest) and I'm afraid the only way to fix it may be to take it to the MB dealer in Madison or an hour away in Loves Park and have them hook it up to the STAR tool.... but was trying to avoid that if possible and thought someone here may have a few easy things to checkf first.

Thanks in advance for any help/suggestions you may have!

Matt

Update. So Drive was working up until yesterday afternoon, when my wife called and said it wouldn't shift out of park. When I got home last night I removed both batteries from under the passenger seat and took them to get load tested. Both batteries were the original. The main battery said charge and re-test, so I stuck it on my smart charger and did a 2 am charge overnight and it completed. I'm taking it to be re-tested today so I'll keep you posted.

Question: How do you test the auxiliary battery, or I should probably just replace that also as both batteries are over 6 years old, right?

Thanks!

it is not your batteries

Finally have an update and resolution: So I had replaced the battery and auxiliary battery to no avail. We were using it as-is sparingly until January. It got really cold for about a week and it wouldn't start after that, we figured it gelled up in the fuel filter or something like that. I said to heck with it as we were moving in February and just trailored it over to my wife's uncle's shop where it sat for a month.

Then we took it to a MB dealer and had them diagnose it. They said the no-start condition was a plugged DPF filter and wanted almost $3600 for that, there were 2 oil leaks (oil cooler and vacuum pump to the tune of $4000 and $2250 for the SCR heater for the DEF fluid.

I had purchased a new ITC transfer case on ebay for $1200 and installed it myself prior to taking it to the MB dealer, as the chain was skipping the sprocket for a few months and it was getting pretty bad. They quoted $1100 to fix the reverse issue and said it was the shifter handle but also had the ISM module listed.

In short they wanted just under $12,000 to fix it all. I said thanks, but no thanks I'll pay the diagnostic fee and see what I can do.

In short. Hollowed out the DPF, sent the ECU off to Malone Tuning and had them turn off the SCR, DPF, EGR, and swirl flaps. Put the filter and ECU back in place and viola! It starts, it runs, it goes forward and reverse works great now too. We've put almost 500 miles on it in just over a week, even hauled a bunch of plywood and wood home from Menards.

I starts easily and purrs like never before. We'll see what we get for mileage, I'm taking the first tank with a grain of salt as it had all kinds of good stuff in it. Diesel 911 and pre-winter diesel fuel. So we'll see what it gets starting with the next tank. It's averaged 20.5 mpg combined for the 25,000 + miles I've checked it.

So it must have been a combination of the old transfer case being bad and clearing the codes on the ECU, as I tried reverse after they got it running and the new transfer case was installed, and it still didn't work at that point.

Thanks!

Your ism (and possibly stalk) will act up again.

You have been warned

hi am facing same issue MY GL350 2010 MODEL not going for reverse gear and engine sometimes start and some times fails to start

Pls let me kniw if you found any solutions

So…don’t be like OP and ignore the very correct advice @alx is giving here.
Guy keeps spouting parts cannon logic when told three times what the issue really is, don’t do that.

That never, ever, happens here Max 😃. I must admit I do enjoy seeing that fella that ignores good advice like it was never provided until they've gone a month without wheels and they finally reach the same conclusion.