Today the speedo went up/down few times then carked it. I put it in dash diag mode & theres no speed showing in there or the trip computer L/100km.
Thinking it may be the VSS on tranny, can this be confirmed with a ohm meter in ecu pin 58 VSS input & body earth? or what type signal would it be & what do I need to test it? she's a EF i6 auto

Check the two white wires on the right side plug of the cluster. If they're okay it's probably the speed sensor then and that I cant help you with sorry. While wiring up a speedo corrector one of the speedo wires popped off and I got similarly weird stuff happening as well