Program a Keyless Entry for a Chevy Silverado

Instructions to program a keyless entry remote for a GM Truck i.e. Chevy Blazer, Avalanche, Tahoe etc. Also works on 2003, 2004 and 2006 GM models.

Steps

Close all the vehicle doors.
Insert the ignition key into the ignition lock cylinder - do not turn ignition switch.
Press and hold the Door unlock switch (this is the switch on the door, not the remote).
While holding the door lock switch in the unlock position, cycle the ignition on/off, on/off (3 times). For Chevy 2002 HD, 2003 Diesel Duramax 2500HD and 2005 Z71 only cycle 2 times.
Release the DOOR unlock switch. The doors will lock and unlock one time to confirm the program mode is actuated. Remove the key from the ignition.
On one remote Simultaneously press and hold the LOCK button and the UNLOCK button for approximately 15 seconds, the doors will lock and unlock to confirm the programming of that transmitter.
Repeat the previous step to program up to four transmitters. Reprogram all existing remotes at this time as they have been erased.
Turn the ignition switch to the ON (one more click forward) position in order to exit the keyless entry transmitter mode.The doors will lock and unlock and the horn may honk twice.
Operate the transmitter functions in order to verify correct system operation.

Also works on 99-2002 Silverado
On an early 2004 Silverado, cycle the ignition 2 times.
On a 2003 Silverado 2500HD, cycle the ignition twice rapidly, do not wait for gauges to come on.
On a 2005 Suburban, cycle the ignition 2x
Also works on 04 Silverado
Also works on 99-2002 Sierra
On a 2006 Silverado 2500HD, cycle the ignition twice rapidly, do not wait for gauges to come on
works on 2005 GMC Envoy SLT XL
Also works on 2004 Avalanche with #1 and #2 remotes
Also works on 1999 GMC Sonoma
Could not get it to enter program mode on 1999 Chevrolet Suburban LT
Works for 2005 TrailBlazer too.
Also works on 2002 Suburban
Make sure to do step 4 fast. After may tries it worked doing this quickly.
Works on 2003 Chevy blazer
On a 2006 Suburban, the first key less entry programmed will set to Driver 1, and the second to Driver 2.
On a 2003 Envoy XL, cycle ignition 2 times
Also works on 2003 Astro LT
On 2002 Trailblazer, cycle ignition 2 times. Thanks for saving me $50+