2004 Trailblazer EXT 4wd 4.2 V.6. Will not engage 4hi or 4lo, awd and 2hi work. The lights on the selector Switch stay lit in whatever gear you choose and I can hear the motor but will not engage the front axle in 4hi or 4lo. Also the cruise control stopped working. I have changed the front actuator and. Changed grease/differential fluid and also checked all fuses and relays.