Codes 12, 53, 91 Sedan Deville 92
 

Need help with this problem, I'm new to Cadillacs:
Service Vehicle light and CCR light on
While driving, speedometer quits and vehicle seems to be in 'limp' mode, runs smooth but with much less torque although cruising speed not too bad
If car is stopped and restarted problem remains but occasionally, evidently randomly, the condition goes away while driving, full power returns, speedometer works again, etc

Codes read with an Autoxray 2000 with OBD 1 cable and unit configured for GM, with 4th VIN #C and 8th #B:

Code 12 "No reference pulse detected" -shows up very frequently
Code 53 "Distributor signal interrupt" - shows up about 1/3 time
Code 91 "Park/Neutral Input Neutral Input Problem" more than half the time
Code 52 "Keep Alive Memory Reset" -once

Oil recently changed, after problem started. Change oil light did go out
After resetting codes engine surges at idle for about 10 seconds, but not if in gear
Some codes do not seem to re-appear unless the car is driven around the block
Thanks for any point in the right direction, I'm looking for a troublehshooting tree or something

RE: Codes 12, 53, 91 Sedan Deville 92
 

Check grounds at engine, battery cables and grounds near alternator.