maurim3

Hey Im new to the forum !

This is whats been happening to my w204 2010 C300. I lock the car at night and when I go the next day and try to unlock with the remote it wont do anything. If I get out the metal key and open it with that, the alarm will start to beep. And after that the remote works perfectly, to lock and unlock.
Any ideas?

SoCal208

Very 1st thing to do is replace the battery in your remote keypad (CR2025 battery). Search youtube if you do not know how to replace the battery. Good luck.

maurim3

Thats the first thing i did. Yesterday i left it unlocked. And today the remote wouldnt do anything. Lock or unlock. I opened the car and it started as usual. After that the remote worked perfect again. There are no stored codes.

maurim3

bump !

Glyn M Ruck

Have you had your car windows tinted recently? What is your radio reception like ~ especially AM? The remote uses the same antenna in the rear window. How does your spare key operate?

Have your car's battery properly load tested.

mike82212

My C300 is a week old and I have Keyless go. Sometimes it wont unlock and sometimes the dash tells me key not found when I try and start

So far, whenever I lock or unlock with the remote all seems ok

Glyn M Ruck

Never leave the key within communicating distance with the car or the battery will go flat. (Keyless go only)

mike82212

I don't. The house is some distance from the car. I walk up to the car and it won't unlock with the keyless feature. I have gotten into the car and try and start it and I get "key not found"

As I said, if I lock and unlock with the remote, it seems ok then

Glyn M Ruck

Wierd. You're under warranty so get the dealer to sort it.

mike82212

Thanks, I was just checking to see if anyone had any ideas. And I know it won't happen with the dealer!

samaritrey

You have tested with a spare key right? Keep us updated my dads car did that the other day (keyless go)

maurim3

AM works great. I dont have a spare key. And the tint has been there for more than 1 year.

maurim3

This morning as usual the car wouldnt open with the remote. So i tried something a friend told me to do. I pressed the trunk lid´s handle or switch, like if was going to open the trunk. And after that the remote works perfectly again. Its like the system was asleep and it woke up when i pressed the trunk switch, the alarm did not activate like when opened with the metal key.

Glyn M Ruck

You might just have answered your own question. The Canbus is supposed to go to sleep & awaken when you open the drivers door etc. However the remote lock/unlock is supposed to remain active & wake up the Canbus with a push of the key button. Sounds as though the whole system is sleeping.

Have your battery checked. Low voltage can cause all manner of gremlins. If the battery is OK you need to get the car onto a Star to check out the Canbus. Quiescent & wake up.

maurim3

Thanks ! i will take it to an indy shop that has a STAR. I have to tell them to check quiescent & wake up on the can bus? its an option on can bus?

Glyn M Ruck

Yes to the first part of the question. No it's not an option - With a Star they can detect the various states of the Canbus & if there is a Canbus short etc. The EIS is the top of the control pyramid. Lets hope the issue is not there.

Catchme26

Same problem anyone knows what was reason?

Chastity

Having the same issue as well. Any quick fix before I take it into the shop?

CaliBenzDriver

05mn: Change the fob battery
15mn: Reboot the car systems
25mn: scan the car for faults

Other options take too much time. Best to let the shop deal with it.
✌️

Chastity

Thanks for getting back. It appears no one has ever shared their follow-up solutions here.

As for my problem, it was my key fob. Even after changing the battery, it didn't respond. What's peculiar is that whenever I opened the car manually with the key, the alarm would sound as expected. But even after getting inside and pressing the lock button to deactivate the alarm, the door's unlock button still wouldn't respond so I thought it was some circuit issue within the vehicle.

But when I tried the spare key fob, voila! It functioned perfectly!

CaliBenzDriver

I used to have same thing happen to me as well !!!

1. You unlock the car,
2. all locks pop up nicely
3. you open the door to get in...
4. then the alarm honks at you, thief!!
5. It's unlocked but the alarm still triggers

That's how I got interested! I took my new MB apart piece by piece like my first bicycle....
I found simple solutions for DIY'ers to cancel chaos for freee

Here it sounds like the Electronic Ignition Switch (EIS) is seeding chaos >>> Solder iron + Reboots prove good medicine.