2008 Ford Taurus 3.5L Engine P0352 and P0446 Fault Codes - Diagnosis After Coil Replacement

I recently purchased a 2008 Ford Taurus with a 3.5L engine that is showing both P0352 and P0446 diagnostic trouble codes. The vehicle runs roughly, and the dealer mentioned it had not been tuned up yet. I replaced all six spark plugs and ignition coils. After clearing the codes, they returned shortly after. I tested continuity on each coil using a multimeter, with readings ranging from 0.004 to 0.006 ohms for Coil B, and 0.002 to 0-01 ohms for the other coils—consistent with normal values. Using a test light, I observed a weak signal between the two wires on each coil, with the weakest response on Coil B. I do not have a noid light available, so I relied solely on multimeter readings and test lights. The purple wire (common to all coils) appears to be receiving power across all coils, but I am getting ground on every coil. A previous owner reported that a fuel injector connector was replaced incorrectly, and the wiring for Coil C was cut and taped back together improperly. I inspected this connection and repaired it using heat shrink tubing at both ends. I also tested and replaced the wire for Coil B, but the issue persisted after reconnection. Despite completing all recommended diagnostic steps, the P0352 and P0446 codes remain present. I am seeking advice on possible next steps—could this be a PCM issue or a wiring harness fault? Any insights from owners of 2008 Taurus 3.5L models would be greatly appreciated.