I grounded pin 13 and when ignition was turned on 4h and 4L buttons flased at same time and the 3 seconds later they did it again. How do I count the flashes?
Thank You

 

As I understand it a single flash means no stored codes, did you disconnect the battery? The resident guru Hanr wrote a helpful guide 4x4 No Worky.... Maybe this will help....

 

 

The vacuum switch is located on the top of the transfercase near the output for the front drive shaft. It has 3 vacuum hoses going to it. It just screws in so u just have to take the hoses off and then unscrew it (I believe it is a 9/16 or 7/16, can't remember). There is a ball in the switch that you should be able to see a large portion of and it should move relatively easy. If it doesn't move easily, or you can only see a little bit of it, it is bad.

Away you can see if the switch is bad without even getting under the truck is get where you can see the actuator when the truck is running and in 2Hi; if the actuator is contracted in 2Hi, then the switch is bad and always allowing vacuum to the actuator

 

For the life of me I cannot seem to see the actuator in action. I will check the vacuum switch. Thank you again for the info. My blazer is my baby, other than my electra glide. I have no patience, that is my problem. I want to think the repair. Why is everything so complicated LOL
Thanks again,
Steve

 

To see the actuator in action, you have to pull the battery and the tray, and then re connect the battery while its out of the tray and such and then watch the actuator. It is def. a pain in the butt, but it CAN be done, haha

Good Luck