vss signal comes from the trans goes to the pcm. from the pcm it goes to the hud, ip, and ccm. if your speedometer works its not likely. the only thing that it could be with the vss signal would be wiring from s215 to the ccm. if you want test the ccm pin g should be no voltage without the brakes, 12v with the brakes on. it would be hard to test the others the vss i think you would need a scope. you could test for continuity from where the vss splits from the speedo to the ccm pin k. if that cruise inhibit wire was grounded or pinched so that it is touching metal it would never work either.
1998 Bonneville SSE
2007 Monte Carlo LT-KYB, Clarion, Polk audio, Kicker
1999 Yukon SLE-KYB, Air lift, Reese dual-cam, Tekonsha
1987 Firebird-355/th400-nothing stock