The CEL is probably just coming on to indicate the low voltage.
The red wire showing 16-19 volts is not good. The VR should be limiting it to 12-14ish.
Did you clean the connections where the subframe rails attach to the main frame? That usually gets overlooked. It doesn't sound like you have a ground problem but more of a VR getting ready to die problem. The volts going down to .06 sounds like something is shorting out (possibly the VR). Be careful, as the over (and under) voltage problems can cook the ECM.
