Re: lost key blues(DIY: Programing Transponder )quote from
Ref:Tundra Mud
DIY: Programing Transponder (The key part that starts the car)
Hello all. Many of us have run it to the issue of having only 1 key for our car. And as we all know purchasing another has it's challenges. Being a Chronic DIYer I found the idea of programming my own keys interesting. And I've successfully programmed and even cut my own key. In fact I've program several transponders. And as is my style, I thought I'd share what I've learned. Might need some editing but if I don't thow this out there now it might never get done.
But first there are many misconceptions about the keys. It amazes me how much miss information is out there. Here is an attempt to shed some light on the subject.
There are two different electrical parts of the key. The part that remote locks and unlocks the doors and the part that enables the car to start. They are independent and, this is important, are NOT programmed at the same time or in the same way. There are lots of posts on how to pair the door locking part to a car. And this makes some believe this will make the car start. It will not. And one can program the key to start the car without programming it to unlock the car. In fact the key could not have the remote unlock part all together. The part that allows the car to start is a transponder. This is the part I will talk about. How to program the remote lock part has been covered in length. And it only takes a couple min to do. The transponder part is entirely different matter.
Myths about the Key transponder and EWS (the part that starts the car)
It can not be programmed - not true
It can only be programmed by the dealer - most dealers don't offer this (maybe none do)
Only the factory in Germany can program them - not true. It just requires special equipment.
The car must be coded or programmed to accept the key - this is for the door unlock portion. Not the transponder, start the car portion.
Once the key is programmed it can't be changed - not true. The key is written to by the car every time it is used. And with a transponder programmer the complete key can be rewritten
Someone could program a key to my car without having the car. - Yes but ONLY if they have the data from the EWS. Which the factory does. And must guard for sure.
There can only be 10 keys for my car ever. - Not true. The factory can only make 10 keys without changing the program in the ews. Saturday I deleted then added back a new key 1 ( I never had key one, I only have key 5). To be clear. Up to 10 total keys can be made without altering the ews at all.
if I loose sync with my key to the car I have to order new keys. - Not true. The key can be reprogrammed just like a blank key. But not many people know how
If the battery goes dead in my key it won't start the car - Not true. Transponders do not use a battery at all.
Things you may not have known about the keys.
The transponder has an EEPROM in it and stores:
The vin number
Mileage at last use
Fixed password
Rolling code (random password)
Key number
New (programmed) keys come with the vin and fixed password programmed. The ews assigns the first rolling code at first use and marks that key slot in it brain as used. The EWS will only provide that key with the next rolling code next time if the KEY supplies the correct rolling code. The ews also updates the mileage in the key. The EWS provides updated mileage and rolling code each time the key is validated (put ion and turned on and passwords are correct.
If one were to duplicate the data in the transponder (have a locksmith make a duplicate of the key) the next time either key was used he key used would get a new rolling code and the other key would cease to work. If you want 2 working keys the duplicate must be coded as a different key in an unused slot and contain the fixed password unique to that slot in that cars ews. Which one can get from reading the ews or having bmw make you a key.
We are DIYers so we don't want to go to BMW, so how do you and I get the info from the ews. It appears this information requires removing the ews from the car to get. One wouldn't want it too easy to get to or it reduces its effect as a theft deterrent. After removing the ews from the car the EEPROM can be read using different methods. For our purpose a key programmer is the most useful. Since that is what we want to do.
These instructions are pretty useful:
http://ncs-expert.com/e46-key-programming-ak90-guide
A few things I would change or add to these instructions.
Unless you are deleting keys from slots you only need to READ the ews. There is no need to write to the EWS (if you use an unused slot). If you keep the ews data. You can write another key to another unused slot without removing the ews (like the factory does). I did this the otherday once my key cutter came. I made an entirely new key without connecting to the car at all. Since I had the EWS data stored on my PC.
If you are timid, read the ews. Write the key to a unused slot. Be on your way.
If you are bold. Read the ews. Delete all used keys that you don't physically have.
Perhaps Later I'll write up more on how to cut the actual key. I've learned a bit about that as well. I want to try a few more things before I write up what I learned.
Thaniel
Last edited by Thaniel; 11-25-2014 at 09:22 AM.
Decoding the E46 can bus:
http://forums.bimmerforums.com/forum...an-bus-project
Home made ipod interface using an Arduino:
http://forums.bimmerforums.com/forum...9#post26478499
LS1-E36 build Log:
http://www.ls1bmw.blogspot.com/ (disassembled)
Electric powered E-36 or uh Ev-36:
http://www.ev-36.blogspot.com/ (disassembled)
Electric powered E46 in progress
