alewifebp

My car was out of service for about two weeks while it had some exterior damage fixed (minor fender bender), and they also fixed a few other issues (groaning sound from the steering column, and they found a transmission code and had to replace some stuff). They also did the BCM update.

What I have found is that now it is difficult to start. While I could usually start the car by just flicking the key in to the start position, I now have to hold it, almost like I am cranking the car. I'll be going back for service soon (actually, see my other thread on this topic), but I'm wondering if anyone else has had a similiar problem?

DWP

Never noticed any delay in starting our car. How long do you have to hold the key in the start position? The only question, so far as the car is concerned, is whether it is getting a "start" instruction, which should be a binary, "yes-no" question. If the answer is "yes", the computer takes over and executes the "start" sequence. Perhaps the battery in the key is getting weak and the car is having trouble "reading" it? Do you have any trouble locking or unlocking the car from a distance too? Beyond that, I don't know; sounds like an issue for the dealer.

alewifebp

No other issues, but I will try my other key and see if that helps. Whereas it used to be just a "flick", now I have to hold it, but it starts right away, so I have not been able to see how long I really have to hold it.

JimPurdy

The battery in the key is only used to lock or unlock the doors. The recepticle where the key is inserted generates an infra-red signal into the end of the key that is reflected back to the reader. At this point, the key is passive and does not even need a battery. Remember the pre-2000 MBs came with a spare "emergency" key that had no battery and would only start the car.

DWP

Interesting. I knew that the key has infra-red capabilities, since that's how it locks the doors and closes the sunroof from outside the driver's door. That's not a passive function, though - it requires a battery, just like a TV remote. Since the key has to pass a unique code to the car for the car to start, does the key passively modulate the infra-red signal from the receptacle with the unique code in reflecting it back to the receptacle?

JimPurdy

I was told that there is a barcode inside the little cylinder that is read by the receptacle. I have taken apart an old key to look at the "business end". There is a plastic cylinder that has a coil of wire wrapped around the end - the antenna part for the radio transmitter. There is what appears to be a metal slug embedded in the cylinder - also part of the antenna. There are 2 glass/plastic bubbles in the end of the cylinder too. One of these bubbles is clear with something inside that is too small to recognize and the other is somewhat purple also with something inside that is too small to recognize. I am assuming that one of these bubbles has something in it that is recognized by the car.

I have checked and the car will start without any batteries in the key. So, either there is something that is read by the car or one of these bubbles can generate electricity for the circuit in the key so the key will transmit something back to the car.

alewifebp

It must work passively, like E-Z Pass. I had an Accord many years ago, and it also just had a chip inside the key that the car read, without the aid of batteries.

I was working under the assumption that my problem was related to the battery, but they also did a lot of work otherwise on the car. The had found a code in the trans, and did a rework and flash of the software, as well as the engine management software.