Have a problem starting my 09 MC (Auto/tiptronic) after the car sits several days.
Insert the key fob and indicators come on but brake is stiff and ignition does not respond. Display area 2 shows a "key". Tried the other remote with same result. The after several tries, re locking doors etc. It works! go figure???
Is there a pause or delay where new data is being reset in the remote? Once it starts first time it does not re-occur. And does not seem to happen when driving daily. But has occured each time the car has sat unused for several days. Battery?? Once the ignition works there is no indication that the battery is discharged (it fires up quite normally)
Feel I've been lucky to get it started last couple times. Any ideas?

 

Yeah, sounds like the car battery is failing.

Or, very unlikely, the CAS module is failing causing the "key" error message and the failure to authenticate the FOB (hence the no-start condition).

 

Sounds like the FOB battery is failing and not holding it's charge/data. That's why it works fine when you use it every day and not after several days. I would think you can replace those rechargeable batteries. The FOB gets recharged every time you insert it in the slot.

 

The fob battery (in the non-convenience setup) has NOTHING to do with the starting of the car. That function is handled by an rfid style transponder.

 

The FOB battery will cause the the loss of data, such as radio stations and other presets but will not affect the CA lock functions or the starting of either CA or Non-CA cars. It is as stated by strobyprobey above

Also of note is that CA cars the battery DOES NOT charge. It is a replaceable button battery.

Non-CA cars do have a rechargeable battery.

 

Thanks for the thoughts. Do not think it is FOB related as BOTH FOBs would not start the car, and when it did finally start, either FOB worked. Spoke with dealer and he suggested 1) Battery could be failing, but they'd need enough time with the car to see the problem; or 2) It may just be taking some time for the FOB and car to recognize each other and transfer data after several days. He suggested to insert the FOB and wait a minute before starting. I'll try 2) next time and hope its just a slow to wake up issue. Thanks for the input!

 

Very possible problem but then the car would probably not start at all as there would not be enough in the battery to start the car. But anything is possible.

As for needing time with the car. NO they can check for a failing battery with a battery tester and that only take a few minutes. Take the car or battery to most auto parts stores and they can check it for you.

Although anything is possible. This is very highly unlikely as "THE ONLY DATA TRANSFER IS THE KEY SECURITY CODE VIA RFID" and this is not a wake up issue that would be solved by putting the key in the slot and waiting a minute or two.

If this does work then the dealer needs to replace a module or two in the car under warranty as this should not be happening. They should wake up and be fully functional in less than 5 seconds.

GOod luck with figuring this all out.