Keyless Entry

First off there is some great info in these forums! Thanks. I have a question about keyless entry programming. A have 99 Chevy 1500 (old body style) that I purchased a new remote for and have been unable to program. I've tried putting the key in the ignition, hold the unlock switch, on-off-on-off, release unlock switch, and nothing happens. Put a jumper between pins 4 and 8 on the DLC, nothing happens. Thought maybe the ground wasn't great on pin 4, tried a different ground, nothing. Checked the ground on pin 4 with a multi-meter, it was good. Is there something on pin 8 I could trace, or another method I haven't tried? Thanks again for all the great info!!

Awe