There is an easy way to check the basic sensor and electronics are ok. Put the unit on a totally level surface. Enter "Display G force" then "Acceleration G force". Check the C value on the left of the display. It should read zero. Tip the unit up so the dispay is facing upwards and it should read 1g (say 0.9-1.1). Tip it so that the display is facing down and it should also read 1g. It should change smoothly between 0 and 1g depending on the angle it faces.

You can do the same in the cornering G force menu by tipping the unit onto one side, then the other.

You can also try setting it up for a 0-60 time, start with it sitting level and then tip it onto its' front and leave it for a few seconds. You should end up with a 0-60 run in just under 3 seconds.

It should be as close as possible to sitting flat and level in the car.

Is the vehicle data plausible?

Mass doesn't matter so much except for BHP calculation but it's about 1700 plus load for an Omega.

CdA is about 0.3 for an Omega IIRC.
Rolling resistance - who knows? 0.013 is the value on mine.
Tilt factor - mine is set to 0.007
Roll Factor - 0.011
Smoothing 0.004

None of the above will make a drastic difference to acceleration times, though.

I haven't used mine for a while but I got a plausible answer the one time I tried it in the Omega - about 8.1 seconds 0-60 for a simple "floor it in sport mode" launch.

Kevin