I have a 2001 Blazer LT. It has the 4.3 liter vortec and 4L60E auto transmission. It has 151,000 miles. The transmission was rebuilt 22,000 miles ago, and recently we changed the fluid thinking this problem was something with the tranny, it was fine.
When I start the Blazer no dash lights come on except the service engine light. When I run a code scan it only shows the 2 codes that it have always shown which have to do with the emission pump not being there. (I bought it 3 years ago w/ the emissions pump disconnected; OK law does not require it)
Anyways, so no lights are on and it is running, I can back up just fine, but when I put it in drive it doesn't want to go any where. After a few seconds of stepping on the gas and the motor revving it gentle and slowly moves. At some point the lights will come on, but it will never shift into over drive.
I used to be able to keep restarting until the lights came on, but it is getting worse. I have to drive until the lights come on pull over and restart it in order to get it to shift into over drive.
This is my daily driver. On weekends I do some light 4 wheeling. Any help or suggestions is greatly appreciated.

When I say I have no dash lights I also mean the needles in the speedometer and rpm gauges have no lights and do not move.

 

I had a similar problem and it was the ignician switch

 

Really? I had that replaced in August of 2008, not to say it hasn't gone out again, but back then is just wouldn't start. What was yours doing? And thank you for the suggestion, you have no idea how annoyed I am w/ the thing.

 

About the same thing as yours. No dash lights, tranny starting out in 3rd gear, throwing codes for tranny solenoids. I think there is a write up on here to test it by jumping across the switch with a fused jumper wire.

 

this. The trans isn't getting power which it receives through the ignition switch. 3rd gear is 'limp' mode. Make sure you replace it with one that has a lifetime warranty, as they go bad often.

 

the transmission is like he said in limp mode, usually when you loose all lights and gauges this means that the pcm could have been fried, its happened to me and a couple cars ive seen

 

1993gmcjimmyW,
Before you said pcm I had no idea what it was and I'm still not sure. I can't remember the number on the emissions codes but there were, secondary intake malfunction and small exhaust leak. Does that have any relation to the pcm?

And I'll be checking that ignition switch too. Thank you everyone!