91 DeVille dash readout problems

I have been having intermitint problems with the Fuel Data Center read out and the Change Oil Soon light. The FDC will cycle quickly thru the 4 read outs with out the control buttons working. At the same time the COS light cycles on and off as well as the A/C service light comes on. As well, the FDC and the Climate Control read outs will display a "d" and not function. If the blower is on when this happens it will stay on and not shut off. I have found a temporary fix to be disconecting the positive battery cable. When reconnected everything seems to go back to normal. Can anyone shed any light on this problem for me?

I have had the same problem with my 89 deville. You said you disconnected the battery and then reconected and it worked ok for a while?

These cars a susceptible to acting "psychotic" if the computer does not get sufficient voltage. Verify that your battery terminals are clean, grounds are clean and tight, and that the cables themselves do not have internal corrosion. Inspect for bulging under the cable insulation near the battery and flex them listening for "crunching" sounds indicating internal corrosion. If you find that, replace the cable.
FWIW
YMMV