just got a 03 2500hd, the guy i got it from is being pretty open about whats wrong with it and is a friend i went to school with. i haven't had the chance to look at the truck real well and haven't had a chance to experience the problem my self so ill try to describe it from what hes said.

Apparently it has a random "no start" issue where it will crank and start then die within seconds. to me almost sounds like a 90s chevy VATS issue but with these trucks i have not that much experience with. but it sounds like he'll do a security relearn by unhooking the battery for 45 minutes and it will start up. i dont know if this fixes it 100% of the time but it sounds like it does. it also has a service air bag light and it also says battery system not charging, but not sure if its related. he replaced the BCM and it did not fix the issue.

 

just to add more to the list of odd things. the radio will stay on all the time unless you pull the fuse. you can reinstall the fuse and it wont come back on till you use the ignition again.
the dome lights wont work unless the key is in the "on" position

 

From the details you provided, it sounds like there could be a few different issues at play. Here are some steps you can take to diagnose and potentially resolve the problem:

1. **Security System**: If the truck starts and then dies shortly after, it may be linked to the security system thinking there's a theft attempt. The battery disconnection for 45 minutes that your friend mentioned may temporarily reset the system, leading to a start, but may not be a long-term fix. If the security light is blinking, it indicates an issue. Consider performing a security relearn procedure or checking the ignition switch and wiring for faults.

2. **Battery and Charging System**: Since the vehicle has a "battery system not charging" message, it's essential to check the battery’s condition, cables, and connections. A weak or faulty battery can cause starting issues, and if the alternator isn't charging the battery properly, that may also lead to erratic electrical behavior. Make sure to test the voltage at both the battery and the alternator.

3. **Airbag Light**: This might not be related to the no start issue but should be addressed. Check for any trouble codes with a diagnostic scanner to see if there are issues that need resolving, especially around the airbag system.

4. **Radio and Dome Light Behavior**: The odd behavior of the radio and dome lights may indicate BCM (Body Control Module) issues, especially since the BCM was recently replaced. Ensure that the new BCM is compatible and properly programmed with the vehicle.

5. **Wiring and Grounds**: Check for any damaged or corroded wiring or poor ground connections throughout the vehicle. Sometimes, issues with grounding can lead to a variety of electronic gremlins, including those you're experiencing.

You may want to consider running diagnostics with a professional-grade OBD-II scanner to retrieve any trouble codes from the vehicle's computer, as this can provide more insight into what might be malfunctioning.