02 pt fuel gauge problem

Hi all. I recently installed a engine compartment complete harness to fix a open for the PCM FLD circuit to the alternator and a intermittent cruise problem, also replaced the PCM with a plug & play. now everything is working and problems are corrected but my fuel gauge goes to full when key is turned on and a few seconds later goes to empty and low fuel light comes on. did self test on cluster and checks good. seems DB wire from tank unit to cluster is open. but I have grounded the DB wire and gauge does same,also does same with DB wire unplugged,gauge worked perfect before repairs were made. need help, car is jacked up with RF & RR tires off ground and has been like this for 2 months. is it possible the cluster has to do a relearn by driving? what else could it be:horse:
Author: boatmoter