Note On INTERMITTENTS
WARNING: This page is about a different car, the 1992 Oldsmobile Toronado. However, it is still accessible from the selected car via links, so may be relevant.
Manipulate related PCM and BCM wiring in each gear range while looking for a change in ED31 or BD41 display values to check for intermittent open or short to ground. Also check terminals for good contact at PCM, BCM and PRNDD21 switch. If good contact exists and Code B127 continues to set, replace PRNDD21 switch.