Citizen_GDD

I just got my 2004 S500 detailed and put it in the garage as the temperatures dropped for last 2 days.

I went out to start it up and received a "Key Not Recognized" alert. Car would not start with Keyless Go or with fob in ignition. Tried both keys, same result.

The lights eventually dimmed until dash was completely dark. Car would not lock or unlock. After 10-15 minutes, car would lock & unlock with either key fob, but still will not start.

Any advice or suggestions for troubleshooting? Battery issue?

It was 35 degrees when I had it detailed, but dropped to 15 overnight Saturday and down to 6 by Monday morning. Not sure if this has anything to do with the issue, but providing as background just in case. Car was operating fine immediately after detail.

wallyp

Battery is certainly a good possibility for the cause of the problem. At six degrees, the battery will only put out 35-40% of what it will at 75 deg. If it is a little weak when warm, it will be toast when frigid.

There also are numerous reports of extreme cold causing problems with the EIS, but I would try a warm, fully charged battery first.

Citizen_GDD

Had to go through the whole process of opening the trunk via passenger seat boost.

Volt meter on battery registering at 5.6. Unable to jump start with booster, though did have interior lights for a moment.

Now key will not turn at all in ignition. Calling AAA to see if they can get it jumped so I can take it for a battery replacement.

Citizen_GDD

Called AAA. They came out & installed a new battery, hooking up memory saver prior to install. Everything back in working order.

When I purchased the car, the power trunk was hit-and-miss and the soft close doors were not working. Was told there was an issue with the vacuum motor. With new battery, trunk and soft-close doors working like new. Battery was old. Looked like it may have been original battery (no date sticker).

Thanks for the help.

wallyp

If one of the pneumatic actuators is failing, and takes more time to function than the allowable amount programmed into the PSE (Pneumatic Service Equipment) computer, the computer will stop trying to operate that actuator.

If one of your functions, the trunk soft-close, for example, stops functioning soon, that usually indicates that actuator is leaking or otherwise failing.

To reset the PSE computer, go to the right rear passenger position and find the floor lamp mounted behind the passenger's heel. Pry the lamp housing from the wall and find the yellow 20-Amp fuse near the inner end of the row. Remove it, then put it back in.

yovenim

Just returned from a month away with the army I'v come back and my car won't start appears to be completely dead won't even open manually key still lights up when I press the button and neighbours say alarm has been going off what can I do???? Help please anyone

S_Holford

Can you open the trunk with the key? If so, charge or replace the battery.

wallyp

First - and important - ALWAYS have the model, the model year, 4Matic or not, and the market where the car was originally sold, in every thread. Easy way is to put it into your profile. But we DO need that information!

Opening the trunk with the metal key is not as simple as it would seem. As Mercedes Benz often makes switches and systems do more than one function on the S-Class, the trunk/boot key lock does more than just unlock the lid.

If you insert the metal key up into the lock, then turn and push up, it will unlock the lid. Sounds easy - but it is very likely that it has been years - if ever - since the manual lock has been turned. A spray lubricant may be needed. Pushing down on the lid as you push and turn the key can be helpful - as can an assistant.

But it is a little more complicated than that. If you push up and turn the key in the opposite direction, it does NOT unlock the lid. Instead, that disables the pneumatic unlocking function on just the trunk lid. Yep. It does. This is to keep the valet from rummaging through your trunk to see if there is anything that he/she wants. To restore the pneumatic function, you have to insert the metal key, then push up and turn in the unlock direction.

Once you do get in, it is best if you can disconnect the battery and fully charge it. A jump start will work, but is a pretty bad stress on the car's electrical and electronic systems. Mercedes did learn better - the wife's 2007 GL450 has a positive battery cable under the hood - much better situation.

I have thought several times that it might be worth installing such a terminal, and running a 10 or 12-gauge wire to the battery cable on the starter solenoid on the S-Class.

You may have to do several reset operations on things like windows, sunroof, steering sensor, etc., etc.

In the future, if you are going into active service for an extended time, a good battery maintainer would be a great idea.

Good luck.

tusabes

Apply power under passenger seat , so you can then pop your trunk electrically heres a video


don’t jump start the car using that power hookup

just give it power so it’s enough to pop the trunk . Then you can either change your battery in the trunk (recommend a new one if it’s old ) or jump start the car directly hooked up to the trunk battery