SGII - IGN gauge question

[abogart]

I understand that the IGN gauge on the ScangaugeII reports the amount of timing advance. On the Corsica it consistently reads about -29 at cruise. It will go up to -18 or so at idle, and all the way to -34 during deceleration in-gear (auto). From what I have heard from other SG users, this value should always be around 0 or higher to indicate timing advance. When I plugged the SG into our '05 Grand Caravan, it read between -2 and 10 in park just playing with the throttle.

Is this normal for 3100's? Is my timing really retarded (no pun intended)?

From what I understand, the ignition timing is completely electronic on these engines, and I don't think there is any mechanical means of adjusting it.

Update: After watching this gauge for a while under varying conditions, and doing some research on timing advance, I have concluded that this gauge represents spark firing degrees before TDC, not directly the amount of ignition advance, as stated in the manual. At least that is what it represents on my vehicle. This makes sense when cruise is normally -30 (30 degrees before TDC), under acceleration it drops to -24 (retarded due to increased intake charge), and -14 at idle (less advance due to lower engine speed).