Voltage Spike After Upgrading Battery Cables

I installed the Big 7 kit from jeepcables on my 98 XJ (4 door, automatic transmission) this weekend and now I am having a voltage issue. About 30 seconds after shifting into drive, the volt meter shoots up to 19 and stays there until I turn the jeep off.

The internet tells me it is probably a ground issue so I removed all the grounds, cleaned them up and re-attached but the issue is still there. Next I thought it was an issue with the alternator field wires but I am getting continuity from the terminals to the PCM. I then replaced the alternator and no change.

I have never had a good grasp of electrical systems. Thankfully I haven't run into any issues up to this point. What should I be looking at? How do I test the grounds to ensure that they have proper contact?

I did notice that the insulation on one of the PCM wires at the G101 ground was torn. I am planning on splicing in a new wire and terminal but waiting for supplies to get here. Could this have anything to do with the voltage spike?

Also, I had to jump the battery because it had been sitting for so long. I am assuming that a battery issue would cause low voltage rather than high.

Thanks for any advice

So did you ever track this down and solve it?

If the 1997-2001 dashboard gauge shows 19 volts, there is typically a connectivity problem in the charging system. Look and test for: a bad ground, a loose connection, chafed or melted wire insulation, a corroded connection, or internally corroded wires.

If the 1997-2001 dashboard gauge shows 9 volts, there is typically an alternator problem, most often worn out brushes.