This is a DIY for all of you who want/need to replace your BCM. This covers specifically 2003 G35 Coupes. It may be similar on other years and models.
A simple socket set and a few screwdrivers.
My car would periodically not start. It would just crank and crank, but not start. During these no-start conditions, the NATS would activate and the red security LED on the dash would light solid. At this point, the car would go into a crank but no start condition. Letting it sit, or lightly tapping on the ignition column would sometimes snap the car out of this condition, and it would start and run perfectly. The car stayed like this for over a year. Eventually, things got worse and it wouldn't not start at all no matter what I did, or how long I waited. This condition turned into the car becoming literally possessed. I would turn the ignition key to the run position and the the bright lights would flash intermittently, the wipers would come on, the dash lights would flash, and all kinds of other crazy things would happen. Also, I couldn't turn off the headlights or wipers once the key was in the run position.
Lastly, the car would store a P1610 code "lock mode".
BCM Replacment Procedure:
1) Pull the codes on your car if present http://panoramic-3d.ru/forums/5765264-post4.html
2) Using the service manual diagnostic procedures, confirm the BCM is actually bad
3) If you believe the module is in fact bad, remove it. Disconnect your battery before removing the BCM. To remove the BCM, locate it on the driver side of the car under the lower left kick panel. You will have to remove a few trim pieces by hand. Once the trim is gone and the BCM is visible, remove the 10mm bolts securing it. This is a pic from a 350Z, but you get the idea
4) Wait to disconnect the plugs from the BCM until after it is loose. By doing this, you can move the BCM to get at some of the plugs that are hard to reach. You will also have to remove the bracket that secures it to the car, along with part of a fuse panel. Remove the plugs going to the fuse panel. Below is the BCM and fuse panel removed. Note, this is actually the BCM out of a 2004 G35 coupe.
5) Now, remove the BCM from the holding bracket. There are little metal tabs holding the bracket to the BCM's plastic housing. Release the tabs and the BCM will slide out of the bracket. Here is a pic of the BCM out of my 03' G coupe after it was removed from the holding bracket.
6) If you haven't noticed by now, BCMs ARE NOT THE SAME FOR ALL MODELS/YEARS!!! Do not buy a new BCM until you have removed your old one. BEWARE! Places like Ebay list many BCMs as fitting cars that they actually are not compatible with. Make it easy on yourself and wait to buy a BCM until you have removed your old one. Look at the part number on your BCM, and use that to find a new one. You see the part number for my BCM is 284B1 AM810. If the part number for the replacement part you are purchasing doesn't match, don't buy it!
Below shows how a 2003 and 2004 BCM can be completely different.
Example of a 2004 BCM:
Example of a 2003 BCM:
7) After you have a replacement BCM, install it in the car by reversing the removal procedure. Reconnect your battery, and attempt to start your car. The NATS should trip, and the car should not start. At this point, if you are still experiencing any other issues that you had before like described above (like wipers and headlights going crazy) then the BCM was not the problem. If your car is acting normal, and will crank but not start, chances are you have fixed the issue.
8) Here's the part of the DYI that isn't DYI. You have to reprogram the new BCM to recognize your key. You have a few options:
-Go grab your CONSULT-II out of the garage and program the car (If this is you baller, STOP READING. Have your G35 towed to the stealership and trade it in for a GTR.)
-Tow the car to the stealership and have them program the car. (I would not recommend thi$)
-Call a mobile locksmith and have them come out to program the car. (I would recommend this)
I called a locksmith and had them come out to program the BCM. They showed up and programmed the car in under 30 min for under $150 bucks. Make sure when you are choosing a locksmith, that they have the ability to program your car. Make sure you actually talk to a tech who will be doing the work. Many times, you will talk to dispatchers who don't know a damn thing. Some places will send someone out when they don't even have the equipment to do the job, and then still try and make you pay a service charge. Do your research before you pay someone to do this, because not all locksmiths have the ability to program your BCM. After the locksmith programs the new BCM to recognize the key, you should be all good.