C0050 on 2006 Pontiac Montana very Intermittent How to troubleshoot

Question

The problem is very Intermittent It never does it when running but only when you start the vehicle. Then it reads All wheel drive disabled , check ABS system and the ABS light stays on. The vehicle then has only two wheel drive. The next time you start it all may be good.

Answer 1

C0050 Right rear wheel speed sensor circuit,

what you have is a failed right  rear wheel speed sensor , Your ABS module detected the failure,you have just that a intermittent right rear wheel speed sensor.