This involves my 2011 GL550 with 72,000 miles. I'm the third owner, purchasing it with 59,000 miles in March 2022. Since I don't drive it much, I keep it on a battery maintainer.

Twice, the GL550 has failed to crank after sitting outside overnight when temps dropped to 0 degrees. Dash lights come on, power seats and other accessories work (thank goodness). No click from starter relay. Also not possible to shift transmission into neutral with two key actuations/foot on brake/two pushes on gear selector. Most importantly, trying to jump from terminals under hood has no effect. Voltage read 11.9 volts, 14.2 with jumper cables attached.

This happened the first time on November 28 2024. Since I did not know how old the batteries were, I removed both. The auxiliary battery had no charge and would not accept a charge. The main batter failed a load test after overnight charging indoors. I installed new batteries and it started right away.

Same scenario occurred when parked overnight at a friend's home. Jumping had no effect. I pulled the starter relay and switched it with an identical unit in the connection center with no success. The transmission could not be changed out of park. Recalling the same event last year when batteries were replaced, I disconnected the negative cable cable at the battery (again thankful the power seat was operational) for a few minutes. Once reconnected, it started with no issue.

Unfortunately, my MB-specific code scanner is at another home but the check engine light is not illuminated.

Is the electrical system vulnerable if main battery voltage is less than 12 volts? Is there some type of immobilizer that was triggered (hence the reason for the transmission cannot be changed to neutral)? For now, I have a 10mm socket with me to disconnect the ground if it happens again.

Thanks in advance.

 

More information this morning.

Vehicle was outside overnight and plugged into a battery maintainer. Outdoor temp was 5 degrees F on instrument panel, 1 degree on outdoor thermometer for home. Panel lights came on when turned to "Run" position. No crank condition recurred. Red message popped up in central cluster "Drive to workshop without changing gear" and then changed to "Door open vehicle not in park." I was leaning into the vehicle to operate ignition, so the door was open.

Any ideas?

Thanks in advance!

 

Put a little plug-in heater aimed at the key area/steering wheel area overnight. Try to keep it warmer than the outside. Just a wild thought, maybe something mechanically is getting cold and moving slow into a position to unlock something?? Cold grease moves slow Ya, left field thinking, but yours is an odd one.

 

Maybe something to do with the EIS (electronic ignition switch) being too cold? I'm not sure if this matches your situation:

 

It could also be your start relay . In extreme cold guts of relay can shrink causing malfunction. You can try to keep the start relay pulled out and keep in warm place and plug it in when it is cold outside and see if it cranks.

 

Great things to check. Thanks for the ideas. I did swap the starter relay with no benefit.

What's most worrisome when it won't crank is not being able to change from Park to Neutral. The usual two quick turns to ignition position/foot on the brake/two pushes on the gear selector does not allow selecting Neutral. Disconnecting and reconnecting the negative battery cable allows both starting the engine and changing gear selection with the engine off. Has anyone had a failure of the transmission ISM have similar symptoms?

 

Wow! Very interesting.
Thanks

 

Have you checked all other relays for their functions in such cold weather ?

 

Your issues with not being able to shift out a park and not cranking are separate, but could be related

please confirm that you have brand new main and aux batteries?

The aux battery operates the ISM which shifts the vehicle out of park, but only if the main battery isn’t able to.

A failing ISM will not prevent the car from cranking provided you have a good battery.

there is a lot of electric weird going on when one or both batteries are failing.

 

I replaced both batteries 11/30/2024. Disconnecting and immediately reconnecting ground at the main battery let's it start immediately. I can then shut down engine and shift out of park. Temperatures here have been 20-40 degrees and the problem has not recurred. It seems it occurs only at single digit or below temps. Thanks for the info about the ISM. I found the reply above regarding ignition switch issues at low temps interesting. My quick fix for the holiday season is keeping a 10mm wrench in the backseat. Thanks for the info about ISM not being source of no crank. Any other ideas Max?

 

Have your car read out with a bi directional scanner. Interrogate the ISM.

 

Max, I really appreciate all of your advice, on my questions and the others. I would benefit with an education about scan tools. I see Benz Ninja, supposed clones of Star system and others, but wondering about a resource on how to use them. The one I have now is a FOXWELL NT510 Elite Bidirectional and wonder if I'm using it to its full potential.

FOXWELL NT510 Elite Bi-Directional Scan Tool Fit for Mercedes-Benz Sprinter Smart Maybach, Full System Diagnostic Scan Tool OBD2 Scanner, Full Reset Services ABS SRS EPB, Auto Vin, Free Update

Can you recommend a thread on this topic or point me in the right direction?

Thanks!

 

I have the Foxwell NT710, and so far it's been great, at least for anything I've needed it for.

Here's the thread on it, scroll down you'll see screen pics of the NT710
OBDII Scanner Thread