2002 gmc envoy. Brake system failure message,abs light,truck won't start

Hello, Since the ABS system cannot disable the engine, I immediately look for a cause of both issues. The likely issue is that the battery is discharged. Have the battery tested, and make sure your connections are good. You could always try jumping the vehicle from another one as long as the proper procedure is followed: Connect positive last, remove positive first. If all is well with the battery, scan for trouble codes with a code reader that is capable of contacting the ABS system.