Hi Everyone,

Have a road race car I am building and recently ran into a problem. Car was running perfectly fine and had no issues. Disconnected the battery, finished a couple things, and reconnected it at the end of day to drive the car out. Car would not start, Security Light is flashing and car will not crank. Attempted Passkey relearn procedure, Lock light will not go out after 10 minutes (Flashes and Remains Steady for over an hour with key on). Attempted with 2 Chip Keys, both of which worked fine before this. When turning the key to the crank position, the dash goes out (normal), and there is an audible click from the BCM. Once I return the key to the run position, the dash returns lit up with the Engine Light and Security Light illuminated. As of right now the car is not tuned, and I was considering using HP to shut off VATS since this is a race-only car, but am unsure if this will help with these Lost Communication Codes as well. Pull codes from OBD, have the following Current DTCs where it won't start.

- U2105 - Lost Communication with ECM
- U2107 - Lost Communication with BCM
- U2113 - Lost Communcation with SDM
- U2129 - Lost Communication with RFA
- C0845 - Device Ignition 1 Circuit
- B1325 - Device Power 1 Circuit
- B3055 - No Transponder Modulation
- B3935 - Transponder Authentication Error

A couple things to note. I am unsure if some of these DTCs were present before the No Start symptom started. It is possible these U-Codes were all present when the car was running fine before. They are however listed as current DTCs. The ignition switch and RFID Scanner have been moved behind an aluminum dash panel that the key goes through. I am wondering if the Aluminum could be blocking the RFID from reading? I did however put the second key behind the aluminum directly up against the reader/black collar and no change. All BCM and ECM/Underhood Fuses are good and have correct power. When jumping the crank relay, I can make the car crankover (Of Course) but it won't start. I am weary of tuning the car as I have no intentions of tuning the car other than to delete this VATS issue, but I am worried that I have bigger problems than only Anti-Theft given these Lost Communication codes. Battery is brand new, connections are clean and tight, system voltage is 12.5. Airbags are obviously removed as is the Security Module. Nothing from a wiring standpoint has changed other than disconnecting and reconnecting the battery. "Should" the car still be able to run with a communcations error across the GMLAN lines?

Any help is appreciated. I have access to all of the wiring schematics from Mitchell1, but these GMLAN and Lost Communication Codes are new to me and I am unsure how to diagnose. Is it possible these codes would clear after the car was running and the Anti-Theft is simply causing this whole issue? Thanks.

 

Sounds like my problem