I have a 2007 Chev Tahoe.
Description of Problem: Past month engine light came on. Then some days for a short time will go off. When light is on the auto start wont work. Battery has been drained so today I changed the battery and have a total electrical power system failure. Zero power to anything. Last month I put a scanner on it but i didnt save the code. It was related to a “throttle body module” i think. Have been reading about the BCM also so im at a complete loss…
Step one get the battery checked.
No power to anything indicates a problem with the connections between the battery and the truck, probably at the battery since you just replaced it. Or there may be a blown fusible link.
Auto start not working when the check engine light is on is normal operation. Nothing to think about there other than fixing whatever is making the light come on.
Total power failure immediately when installing a new battery indicates something wrong with battery installation or a completely dead new battery.
Check that you’ve connected the battery correctly, positive cable to positive terminal, etc.