[blbrchnk]

Ultimate irony here. I have been getting the car back to stock and cleaning it up to sell. Of course I sold my jb4 as well as my BT cable.

Anyhow, I had the cowl cover off as well as the ecu cover and there was a mix up with a friend of mine, he thought I wanted the car washed. Long story short, the dme had water on the pins. I was out of town so I really don't know how much water got on it. I stripped it all apart and dried it out yet when I put it back and tried to start the car, it gave a bunch of errors and idled extremely rough. Seemed like it would settle down if I have it some gas, but if I let off it, it would shake hard and almost stall out.

I didn't run it long but I think it was also getting warm (water pump not running) as I had the indication on the dash.

I have another Bavarian technic cable on the way to help troubleshoot it, but I am hoping there is some level of salvation for it. Only other thing that happened in between the last time that it ran fine and now is the battery died from sitting for about 4 weeks without being run.

If the dme is toast, what are my options? Buying a used dme and having a dealership program it? Any help would be appreciated.

Thanks

[nate5ks]

First, have the codes read if you can't do it yourself with a BMW specific scan tool. There are a number of things that could cause your problems that are easier/lest costly to fix than replacing your DME. That being said, a bad DME can throw false codes.

Second, the dealer will not program a used DME and there are very few people who have the know-how to do this. The dealer wants to sell you and program a new one for $1000+ because it is more lucrative for them. The reason for this is that the DME has a rolling code (around 20 lines I think) stored in its EEPROM that syncs with the rolling code in the CAS module. Everytime you start the car these two modules sequence to the next line of code. If the codes do not match, the car will not start at all. The codes can be re-synced with some BMW scan tools if a problem causes one module to roll over but not the other but the codes cannot be re-written. The two modules are "married" if you will.

Example:

Good working modules

DME CAS
0001111110000000 0001111110000000
1111111000000111 1111111000000111
1111111111111111 1111111111111111

Modules out of sync

DME CAS
1111111111111111 1111111000000111
1111111000000111 0001111110000000
0001111110000000 1111111111111111

Modules from different cars

DME CAS
1111111111111111 0000000000000000
1111111000000111 1111111111110000
0001111110000000 0001111111111111

There is no way to sync two modules from different cars because the rolling codes are totally different. The only way to get a used DME to work is to flash the EEPROM in your used DME with the BIN file you get from the EEPROM in your original DME. I have seen this work before but you need specialized equipment and some serious know-how. If your DME was water damaged there may be visual evidence of corrosion upon opening the DME but it is a multi-layered printed circuit board and the damage may not be apparent upon inspection. If you have already opened your DME, look for this. After this I recommend scanning for codes and posting them here for review or getting the opinion of a local professional. If your DME is in fact the problem, you can either purchase a new unit from the dealer and have them program it or find someone who knows how to program a used DME. However, these people are hard to come by and admittedly I am still in the process of learning how to do this, otherwise I would be glad to help you.

Or you can get a used DME + CAS but they will need to be reflashed with the VIN number of your car.