R350 – Cold weather starting issue, dashboard lights on but engine won’t crank

Feb 4, 2026 | 06:12 PM

rejson

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W251 R350

R350 – Cold weather starting issue, dashboard lights on but engine won’t crank

Hi everyone,I’m having a serious cold-weather starting issue with my Mercedes-Benz R350 and I’m hoping someone here has dealt with something similar.Even at temperatures around –12°C (10°F) or lower, the car often won’t start after sitting overnight. When I turn the key in the ignition, all the dashboard lights come on normally, but the engine does not crank at all. There’s no real attempt to start — it’s like the ignition or starter doesn’t engage.Earlier, I also had a warning message on the display saying:“Drive to workshop without shifting gears.”Because this seems to happen in freezing temperatures, I suspect the battery might be weak, but I’m not sure if that alone could also trigger a transmission warning.So the current situation is:Problems start already at about –12°CDashboard lights work normallyNo cranking, no startPrevious transmission warning messageHas anyone experienced something like this in cold weather with an R-Class? Could this all be caused just by a weak battery or voltage drop, or should I be looking at the starter, ignition switch, or transmission electronics?Thanks in advance for any advice.

Feb 4, 2026 | 08:25 PM

slawek

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Joined: May 2007

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could be bud ground connection , or weak battery .

Feb 4, 2026 | 09:00 PM

rejson

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W251 R350

Quote:

Originally Posted by slawek

could be bud ground connection , or weak battery .

I’ve started with the battery — I’ve already bought a new one and I’m currently waiting for delivery. I really hope this will solve the problem.

Feb 5, 2026 | 11:29 PM

slawek

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Joined: May 2007

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if your battery was older then 5 years then in the cold weather is no good.

Feb 6, 2026 | 03:05 AM

rejson

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W251 R350

Quote:

Originally Posted by slawek

if your battery was older then 5 years then in the cold weather is no good.

I’ve been driving this car 4 years and I definitely haven’t bought a new battery myself. I also don’t know if or when the previous owner replaced the battery.

The new battery is scheduled to arrive on Monday. In the meantime, the car is currently immobilized and not drivable.

Last edited by rejson; Feb 6, 2026 at 03:09 AM.

Feb 7, 2026 | 10:15 AM

Giancarlof

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Joined: Oct 2022

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R350

Something similar happened to me. One key would not start the car but would lock/unlock and raise/lower windows. Did not get a message about recognizing the key. But when I used our spare key it started right up. I too was advised to change the battery but it was not necessary.

G

Feb 7, 2026 | 02:32 PM

rejson

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W251 R350

I connected the car to a diagnostic computer and it showed errors related to the EZS and ISM, and the faults could not be cleared.
I then removed the radio panel to access the ignition switch, unplugged the wiring connectors from it briefly, and plugged them back in. This allowed the ignition switch to re-initialize, the errors to be cleared, and then I was able to start the engine.

Everything points to an issue with the ignition switch, and it looks like I will need to replace it.