I've been having a problem on and off the past couple of months where my speedometer displays impossible values like me going 6 mph on the freeway and my odometer not showing the correct mileage traveled to destinations(under reading by about a factor of 5-6). I have an AEM infinity and plugging it into my computer I can see that the speed sensor is working because the ECU is reading correctly (checked with speed traps). I have checked the fuses and they seem to be good. The issue seems to show up when I go WOT at times, and goes away when I drive economically. I have read earlier posts saying this is a ground problem with G101, but I was wondering if there could be any other possibilities before I disassemble my head to get to this annoying bolt.
Any help would be appreciated,

Thank you!

 

G101 is where I would start, it is the #1 cause of a lagging speedometer.

 

Is G101 also responsible for an inaccurate odometer aswell?

 

Yes, it will rack up lower miles.