1994 Geo Prizm LSi - 1.8L 4-speed Auto. 145,000 miles

O/D (Overdrive) light flashing once every two seconds when driving.

When in (D)rive car will not start in 1st (Low) gear. Starts in 2nd only and upshifts OK. Same symptom if O/D is engaged or not engaged. Engaging O/D is working - will drop to 3rd if disengaged and visa-versa.

Gear selector can be manually put into Low and and upshifted manually to Drive. Transmission is OK. Fluid OK.

Getting a code 62 and 63 from the ECM. Cannot find any reference to these codes.

Any thoughts on where to begin? Is there a tranny modulator somewhere? Vaccum leak?

Thanks - Jim