OldMacGuy

I've got a 2003 C5 50th Anniversary that I believe I have screwed up royally. Current status is that it won't crank, all other electrical systems seem to work. Current codes are 40-BCM B2723 and 99-HVAC B0446. "Helpful" description for B2723 is "PASS Key detection circuit". The car "FAILS" the first step of the 30 minute TDS relearn procedure - security light doesn't turn off after the specified 10 or 11 minutes - I got frustrated and quit after it was on for 24 minutes. At present, I have NOT cleared any of the codes (current or history).
How it happened:
I have recently reassembled the entire dash assembly after replacing the emergency flasher switch. If I find the moron who designed that switch to be installed from the rear instead of the front, I'll wring his neck!! In the process, I added two circuits by using piggyback fuse taps on fuses 8 and 22 on the cabin fusebox, and unplugged/replugged several fuses trying to find appropriate ones for the new circuits. I also replaced all of the mini ATC fuses in both fuse boxes with the kind that have a LED light up when the fuse blows. Before reassembling the dash facia around the steering column, I wanted to see if I could route the connector wire from the resistance detection contacts in the key switch so they would not get into such a bind when you turn the key to "start". Unfortunately for me, I did not notice that I had not reconnected this wire to the BCM input connector under the steering column, and rotated the key to the "ON" position (not the "START" position 3 or 4 times with the key resistance disconnected from the BCM circuit. After I noticed my mistake and reconnected the wire, the car won't crank. I have had the battery disconnected overnight at one point in the troubleshooting process. I have had the battery fully charged with a 30 amp charger connected during the 30 minute relearn procedure, but the security light won't go off after the specified interval of 10 or 11 minutes in the first step. I quit the procedure after the light stayed on for 24 minutes. I have tested the part of the ignition switch that contacts the resistor in the ignition key with an ohmmeter, and it is functioning correctly each time, every time with the proper key resistance. I had replaced this part of the keyswitch last year after experiencing intermittent operation with the original one. I have located and tested the TDS starter relay located above the cabin fusebox, and it functions properly when given 12v on the low current side. I does not receive a 12v signal from the BCM when you turn the key to "START". I haven't tested the fuel injector relay, but I suspect it is likewise functioning properly. The car is sitting in my garage, waiting to be fixed or dumped into the Savannah River.
I would greatly appreciate any help that is offered.
Tom Varallo@gmail.com

tblu92

Typically a LS1 engine that has a security or "VATS" issue responds this way---The engine will start and then die after 5 seconds----
f your engine won't even crank over--this is probably NOT a VATS issue but rather something else----
Make sure you have the correct VIN number programmed into your installed ECM
Beyond that Even a car with a FRIED ECM should crank over--leading me to believe you have other issues like wiring -ignition start circuit

OldMacGuy

My apologies to all who have read my original post and scratched their head in disbelief. Yesterday, a friend suggested that I check the connection of the resistance sensing circuit near the steering column. While doing so (again), I noticed that the connector for the in-cabin temperature sensor, immediately adjacent to the key switch, is exactly the same connector. I thought to myself that I couldn't be that dumb as to have these connections backwards. However, when I looked harder, they were!! So much for human error!! When I connected these 2 correctly, I turned the key and had instant crank & start !! The car is now cranking and starting fine !!

Thanks very much to tblu92 and my friend who both spurred me to analyze the situation more closely, and not ignore the obvious.