Keyless Go Problem

[Brett]

Missus went out in my car this afternoon (we'd already been into Edinburgh for the day) with one of her friends and our respective kids. She phoned me at 17:15 to ask me what she needed to do to unlock the car! I made a few obvious suggestions and when that still wasn't working, jumped into her car and went to "the rescue".

I took my spare key with me just in case the battery had gone in the first fob. Turned out that none of the buttons on either of the keys worked and I couldn't get the "skeleton" key to work either. So I decided to take the women and children back to their respective houses and called Mobilo Life.

I got a call back within 10 minutes of logging the call and an ETA of 75 minutes from then. I went back to the car a little later (nice cup of tea first) and found when I got there that the car unlocked and locked as normal! I called Mobilo Life back and they suggested that I wait until the technician got there as they wouldn't want me to break down again.

Turns out they'd despatched John Weir's Perth technician to come sort me out. He arrived 5 minutes ahead of schedule and couldn't have been more helpful if he'd tried. He carried out a full diagnostics test, cleared some old codes and re-ran it again. No faults were logged. He then went to unlock the car again and it came up with "Keyless Go card not recognised". We then tried to lock/unlock the car again but it didn't work. Car starts with the key in the igniton, no problem, just problematic unlocking/locking the car.

So off up to Perth in the morning to try find out what is happening. Luckily, I live in the middle of nowhere, so haven't had a sleepless night worrying about the car. Anyone else ever come across anything like this?

 

[amwebby]

Occasionally, when doing lots of short journeys in town, the keyless go won't start the car. The doors unlock fine but no amount of pushing on the gear lever button will start the car. I've always put this down to the short journeys draining the battery, as a good blast up the motorway sees the problem go away. Not sure if this applies here or not but it might be worth checking the condition and charge state of your battery.

 

[Brett]

Not sure if this applies here or not but it might be worth checking the condition and charge state of your battery.

Thanks will check it out, but I suspect that this isn't the case here. Diagnostics showed it up at 11.8v and we'd just returned from a 60 mile roundtrip to Edinburgh.

 

[Ultymate]

Sounds like alternator and or battery problem

 

[glojo]

Hi Brett,
Sorry to hear about your problems. It looks like your doomed to a life of problems with your Mercedes vehicles

Hopefully this is a one off and once again it is so reassuring to hear about MobilioLife coming good.

Not bad for a 'rust' warranty'

Good luck getting this issue resolved,
John

 

[Uky]

This may not apply to your specific Benz, but if the key is the same as for a S/CL then this is one probable explanation. When the handle is touched or pulled, the car sends out a 125 kHz burst to the key. The key answers using 433 MHz with the authorization code. If the car recognizes the code, the door is unlocked. If the key is held close to a cellphone or other electronic device, it might get disturbed. 433 MHz is an ISM frequency (Industrial Scientific Medical) which means that whatever devices there are are allowed on that frequency. It includes wireless headphones, short haul modems and amateur radio operators. While the power of the key is in milliwatts, a radio amateur is licensed (at least in sweden) to use 1kW of power (!) The frequencies around 434 MHz is designated for FM talk channels. In large urban areas, the activity could be substantial. Normally the power is between 5 and 50 watts. An amateur radio operator within a short distance can easily block any remote key trying to reach the car. At least in the S/CL class vehicles, Benz has a spare Infra red system and if disturbed, the advice is to use the infra red functionality by holding the key close to the little lens in the driver door handle. Once again. If your CLK uses this scheme I do not know, but the S/CL does.

If a normal key with remote function buttons is used in the normal keyslot at the steering column it uses the infra red link to verify the code. No 433 MHz is used at that time.

Whenever there is a problem with remote opening: Is it repeatedly on the same location? In a city area or in the country side? Same time every day? People who experience frequent battery drainage are often victims of some transmitter nearby preventing the vehicle from entering sleep mode. The remote reciver normally falls asleep when there has been no RF messages for some time. Then the vehicle shuts down the ECU's one after another to reach a quiescent current of a few milliamps. A nearby transmitter can keep the receiver active, thus preventing this. The only way to tell is to measure if the vehicle enters sleep mode sucessfully but it has to be done at the parking spot. Not very easy...

 

[Brett]

Thanks everyone for your posts, especially the lengthy one from Uky. To answer your questions about whether the problem has occurred before, in that spot etc etc, the simple answer is no. My wife was visiting a park to go for a walk with a friend and the kids - she usually uses her car for this. This was the first (and probably the last ) time she has used my car for this.

The car is currently with a dealer who has not been able to isolate the problem. Indeed, the car worked faultlessly this morning with the Keyless Go system, although it did report a low battery on one of the fobs. I shall wait and see what they come back with and will let you all know.

 

[Brett]

Hi Brett,
Sorry to hear about your problems. It looks like your doomed to a life of problems with your Mercedes vehicles

Hopefully this is a one off and once again it is so reassuring to hear about MobilioLife coming good.

Not bad for a 'rust' warranty'

Good luck getting this issue resolved,
John

Tell me about it - at least this one has only one problem Was very happy with the Mobilo Life service last night. The technician that came from the dealer also did them a powerful lot of good. If I get my next service done by them instead of my usual dealer, it will be down to his good service, humour and professionalism last night. I intend to write to his manager to tell him that too.

 

[richard]

Thanks will check it out, but I suspect that this isn't the case here. Diagnostics showed it up at 11.8v and we'd just returned from a 60 mile roundtrip to Edinburgh.

If it was 11.8 when running you have an alternator issue - should be around 13-14V (else alternator isn't charging the problem)

To be honest, 11.8 is a bit low when ignition is off as-well, especially after a 60 mile run - suggesting bad battery - some systems don't work properly when voltage is low - and on my SL i've found some systems turn off when battery is low (parktronic, heated seats, some of the keyless functions, you have to pull the handle to re-enable keyless go opening, rather than just touch it)

The keyless go card and key is now combined into one so you always have a key with you for when it fails !! My original SL did lock me out a couple of times, I had to pull the keyless go fuse to make it work again (it was summer, roof was open) !!

Most systems log 'low voltage' fault in their fault history when this happens

Richard

 

[Uky]

Modern keys has a "lo-batt" counter. If the key battery voltage drops below a certain threshold, a lo-batt counter is incremented once the remote function is used. After a number of remote operations there should be a Lo-Batt message in the DIM (Driver Information Module). Since a Lo-batt condition can occur as a result of cold weather, the counter will be reset if the key is kept warm (like room temperature) within the predetermined 8 times (or so) the next time a button is pressed. Once again, This is a common procedure today, but I can not tell if the CLK uses this scheme.

A steady state battery voltage of ~12.5-12.7 V should be normal. (Vehicle parked, engine off, no lights on). It may be that the vehicle battery is bad. If for instance one cell is bad, the alternator will run continously at maximum power. This will shorten the alternator life. Using a clamp on DC current meter will tell if the charging current is excesseive.

 

[Brett]

Thanks to everyone for their comments - the voltage reading I saw was reading the Star Diagnostics system over the technician's shoulder (so I may have misread it). He did have a spare battery with him but did not think that was the issue. The car was turned off whilst he was doing his tests, but the interior lights were on so he could see what he was doing (not much draw there I would have thought). It was also pretty cold with an ambient temperature of around 2C. Whether that had anything to do with it or not, I don't know.

I too have the keyless-go integrated into the fob. I've had two W220's prior to this which had the separate card, but not this one.

 

[Joe Bagnara]

As suggested by previous coments you need to check the open circuit voltage of the car battery.
Fast idle the car for a few minutes. Turn off all electrics and using a voltmeter read the battery voltage at the battery.
12.65 V indicates full charged
12.24 V indicates half charged
11.89 V indicates zero charge.
Low voltage supply in modern MB cause all sorts of spurious problems.

Joe

 

[Brett]

11.89 V indicates zero charge.

Hmmm, the case is building for a dodgy battery then...I'll call and speak to the technician today...

 

[fuzzer]

i would go with that theory too.

low voltate in my old 530d caused no end of problems.

11.8v sounds low TBH

 

[Brett]

Well, I'm not convinced but they've replaced the battery in the fob and tell me they can't get the system to misbehave. I'm away at the moment so have left it with them until Monday to check out further. I've asked for them to check out the battery voltage and to comment...