4WD electric problem

I have a 2000 Chevy Blazer with 4.3 L A/T 4WD. While I was driving, all the 4WD push button control LED lights lit up on the dash. Stayed on for a few seconds, went out and then the service 4WD light comes on for a few seconds and then goes out. It is starting to do that alot now. Sometimes the engine seems to loose some power when the Service 4WD light comes on.
Actuator under battery appears good. I can still get it to go into 4WD. Actuator moves along with the cable. I hooked up a vacuum gauge on the switch just above the distributor to check vacuum. It pulls 18" when I engage the 4WD, but it will "flicker". It will holds steady at 18 then jump up to 0 like it was shut of then go back to 18" in just a second. It may hold at 18 for a few minutes, jump up to 0 then go right back to 18"
I have cleaned the battery, found corrosion on the positive terminal.
I cleaned the 4 pin connector on the 4WD TCCM down behind the passenger kick panel. Found some corrosion there also.
I cannot find any vacuum leaks.
I think that it is electrical. Is there a way to test the TCCM. I bypassed the electric vacuum switch by hooking the 2 hoses together. No change in symptoms. How can the push button controller and the TCCM be tested?

Had issues with 98. No clue on testing. Mine would drop in/out of 4wd. Replaced the TCCM.

Thanks for the reply. I hope that it is not the TCCM. I hope to have some time this weekend to look over the wiring to see if it has rubbed through the harness somewhere.
Does anyone know where this system grounds. I read on some of the newer pickups that the is a ground wire under the drivers door that corrodes and looses ground.