I don't know if anyone is interested but here is the outcome. I decided to first check the resistance of the circuit at the ECM. The circled connector is where the knock sensor wires are.
The front circled wires are sensor 1 and the back ones are sensor 2.
Sensor 2 measured 5 M ohms and sensor 1 was open. Knowing the outcome, it would have been far easier to skip this part of the diagnosis.
I then removed the front engine cover and the problem was obvious while using a flashlight. The picture doesn't show the problem but looking below the alternator (circled) shows the problem.
The connector was broken or eaten. It is hard to tell being there are no markings on the other part of the wire.
There was enough room to do the repairs on the connector/wire with the alternator removed. Engine power is restored and it doesn't go into Safety Retardation.