S70Houston

Bought a brand new Key Fob at the dealer in May of 2020, which for some reason stopped working.

The car is my son's, who is in the process of getting his license, so the car is not driven much. Therefore, the keyfob is not used much either. Worked PERFECT when I picked it up from the dealer, and for quite some time, started to work intermittently, now stopped working completely.

Put a brand new Duracell CR 2025 battery in it, still nothing. Is it the fuse?

Any ideas? What could be wrong?

Thanks very much in advance

E55Greasemonkey

What, exactly, stopped working? Do you have another key? Does the red LED on the key light up when you press the buttons?

S70Houston

Led button lights up, also the infrared button which can be seen by the camera of the phone works. I therefore assume the Key Fob is good. Lock/unlock button functions do no longer work. (trunk unlock as well)

Car does start with the keyfob

E55Greasemonkey

Sit in the back seat and push up on the headliner where it meets the top of the rear glass, at the same time, try locking/unlocking with the fob.

S70Houston

Ok, then what? What is supposed to happen?

slammer111

Does the other fob work properly? If so, the fob is broken. If not, then there is something probably wrong with the antenna in the car.

The antenna wiring is located around the edges of the rear window. Couldn't tell you too much about the sedan unfortunately.

S70Houston

Have not tried the old remote, but will do.

Saw a couple of YouTube videos, both mention that there is a fuse which needs to be obviously ok (have not checked that yet either), and that there is a process to re-initialize the remote by holding lock and unlock button at the same time, then depressing the lock button five times will holding the unlock?

S70Houston

Ok, after work I checked out the car and did the following:

- Pushed on the headliner where it meets the top of the rear glass, at the same time, tried locking/unlocking with the fob. - NOTHIING
- Checked the fuse in the trunk. - FUSE IS OK
- Tried to re-initialize the key fob as pointed out in YouTube Videos - NOTHING
- Tried the other (old) key fob (which as well blinks the red LED light when pushing buttons and has the infrared light on the front working). - NOTHING

Any other suggestions? I am just puzzled as to HOW this just quit working with the car just sitting under a cover in the driveway?

Guess I need to see my trustworthy mechanic and have him scan for a possible code?

Thanks Guys!

S70Houston

Any further advice here? Or am I going to the dealer?

My mechanic advised that they are not all that advanced when it comes to electrical issues.

S70Houston

Guess I am on my own here.

E55Greasemonkey

I hear crickets....chirp, chirp.

The only thing you can check is the antenna amplifier where I told you to press on the headliner. It is attached to the rear glass with double sided tape and the soft conductive contacts press up against the antenna lines on the glass. The amplifier sometimes will become loose and lose contact. Last I heard, MB no longer sells them, but in theory could be repaired with (new) double sided tape.

Any other diagnosis will require Xentry/DAS and a knowledgeable MB tech who knows these older cars.

No, I'm not flying out to Cali!

https://www.google.com/search?q=w203...w=1536&bih=809

S70Houston

Many thanks Greasemonkey.

I think I will have to have the local dealer diagnose the problem.

You sure you don't want to come out to Cali? I will buy you a beer (or two). 😀

PDs2007C230

So in the interest of helping others what was the solution.

S70Houston

Have not addressed the issue just yet. Hoping to get around to it in the next weeks.

Russell Ormerod

Key not working or starting the car.. problem can only be with EIS then. Are the km being displayed? Next step. Plug in DAS and check faults

S70Houston

Thansk.

Everything works, other than the lock/unlock feature of the keyfob for doors and trunk.

- Car does start with the key/keyfob with no issue.
- All displays work as they should, no problems whatsoever.

Russell Ormerod

Okay.. So did you try pointing it to the door handle to test if IR works? Fuse 8 in rear sam ok? Disconnect battery for a min to reset the remote signal stored in the rear sam

S70Houston

Please excuse my ignorance, ...... IR? What is IR?

Fuse 8 in the rear Sam? What is the rear Sam? So there is a Fuse 8 I need to check?

I should disconnect the battery for a while? I did not try/do this.

Any additional, more descriptive steps to take care of this issue are most appreciated, thanks very much.

Russell Ormerod

IR is infrared. Point the key toward the small black square in the door handle. Rear sam is the rear fuse box in the boot

S70Houston

Thank you.

So how do I know if the IR is working or not? If I put the key very close to it, the car should lock/unlock?

Thanks very much for your time.

scott414

easiest way to tell if the IR works is by using the camera in your phone, turn camera on, then using the remote, push the button, if it working you will see a light flashing on you camera, no lite, then to remote is bad

S70Houston

If you guys scroll down to the beginning of this thread, I have already done most of what has been suggested.

The one thing I did not do is disconnect the battery, which I will attempt to do this afternoon, in the hopes this may help to correct the problem.

7/25/21:
"Led button lights up, also the infrared button which can be seen by the camera of the phone works. I therefore assume the Key Fob is good. Lock/unlock button functions do no longer work. (trunk unlock as well)"

7/26/21:
"Ok, after work I checked out the car and did the following:

- Pushed on the headliner where it meets the top of the rear glass, at the same time, tried locking/unlocking with the fob. - NOTHIING
- Checked the fuse in the trunk. - FUSE IS OK
- Tried to re-initialize the key fob as pointed out in YouTube Videos - NOTHING
- Tried the other (old) key fob (which as well blinks the red LED light when pushing buttons and has the infrared light on the front working). - NOTHING"

S70Houston

Just went out to the car and checked the following:

- IR on keyfob works, when looking through phone camera.
- Fuse #8 in the trunk is good.
- Disconnected battery for a couple of minutes and reconnected. Unfortunately, this did not make a difference either.

When holding the keyfob super close to the black square on the door handle, car locks/unlocks with no issues. Everything else still works as before.

Any more thoughts? Why does the car not receive the signal from farther away?

Thank you all.

Russell Ormerod

Did you check fuse 8?
Did you disconnect battery?
if that is done then your antenna amplifier is probably faulty. Or even a faulty remote!

S70Houston

Did you read below?

YES on both!!!!!!!!!
Checked the fuse and did disconnect the battery.

Keyfob was purchased new from MB Dealer 1 year ago.