How do i change a 4x4 module 2002 trailblazer?

when i switch to 4 hi lo or awd the light flashes and i can't hear the 4 wheel drive try to engage. what do i need to replace solenoid module the switch seems to be doing it jobHow do i change a 4x4 module 2002 trailblazer?well you might not hear the 4x4 engage. check with your owners manual to make sure you are engaging it the right way. meaning, should the truck be in park or neutral, ect. if you are doing it properly, which you probably are, then try driving it in AWD. you will know if its in AWD by going in circles. the tires will skip and the truck will buck. then try it in 4x4 low and do the same. if its not working you will have to take it to a shop. really the only way that you will know whats wrong with it is with a scanner. using a scanner, the mechanic will check the sensors and much more. it will be easier to have a mechanic find out whats wrong with it first, then you can replace the sensor or the module. i worked on a trailblazer before with the same problem and around the same year. i diagnosed the problem being a output shaft speed sensor because i was not getting any info from the sensor. but what it ended up being was the control module. it has a control module behind the passages kick plate. it was bad and that's why i wasn't getting a reading from the speed sensor. Good luck.How do i change a 4x4 module 2002 trailblazer?It souds like your moduleand if i remember right it's bolted on top of the passengers side crankcase, just need to unbolt plug the wiring ,then remove the bolt that's holden it in.