2005 Cadillac STS

Computer problem
2005 Cadillac STS 6 cyl Two Wheel Drive Automatic 72000 miles

I have a 2005 Cadillac STS with 3.6L V6 and 72k miles. When brake and Start Button are pushed the dash goes black, but interior lights stay on, and will not crank/start at all(no clicking, no nothing). After 10-15 seconds, dash lights come back up as if car is running, but engine has not started. All interior lights and guages appear to be working properly. Tried jumping the car, no go. Took the battery to be tested and it tested ok but I purchased a replacement just to be sure as the dealer had replaced the battery under warrantly just 2 years before when this happened. The car still will not start. I checked the codes and only get one trouble code, U0100 " Lost communication with Engine Control Module/Powertrain control module A.&Quot; I have seen several other posts on other sites regarding starting problems, but curiously, no one has posted their final resolution. Thanks.
June 8, 2010.

I can try to help you with this, I can't guarantee a resolution without being able to put my hands on it. Which module set the U0100 first of all, and has communications been established with the ECM(data display and codes from the ecm itself)? I know you mentioned jumping the vehicle, but has it experienced a low voltage condition? Have you tried disconnecting both battery cables, and shorting them together for a minute or so. This accomplishes a reboot of the system, discharging the capacitors. If you have a module that is logic locked, it could cause the symptoms you are describing.

Jun 9, 2010.
Hey Jazzaro1 I have exactly the same problem my car is currently at the dealer. Did you got your car working and what cause the Code U0100? Please help thanks in advanced!

Jul 4, 2012.