No signal from ALDL - Scanner won't read

I have a 2000 Blazer LS 4x4 and the SES light has come on, but scanner won't even initialize when connected to port. Has anyone else experienced this before? My truck runs as well as it ever has, and I can't get the code for the SES. Any ideas?

Thanks
Travis

Aha! I found that the cigar lighter 15A fuse was blown, possibly related maybe. I will take to get scanned again and see if it will read codes now.

Turn the keyswitch on after plugging in the scan tool.

After replacing that cigar lighter fuse, the scanner was able to pull the codes. It showed a P0410 and a P1416. So based on what others on this board had posted ( thanks muddog) I removed the air pump and it was full of water. After a thorough drying, I replaced the 30A maxi-fuse that was by the battery and fired up the engine.

The air pump spun freely and blew a surprising amount of air for about 30 seconds. I did this test 8-10 times and then I hooked it all back together and cleared the codes. I extended and rerouted the air pump intake hose so that it runs behind the battery and into the fender.

Hopefully after some driving cycles the SES light remains off!

Thanks to all the contributors on these boards.

Travis