[Mark Ruset]

i was a GM service manager for many years, when we would see problems like this we usually found that the pin tension on the harness was not adequate for a proper connection. It is very important that you probe the terminals with the proper pin connectors, if someone used a test light or an ohm meter to check for continuity than they may have spread the terminals just enough to make for a poor connection. Make sure your shop has the proper tools to diagnosis this concern.