Hello- wild situation with a 4l80E need opinions

[Six_Shooter]

1) The four wires from the distributor are labelled REFerence, EST, Bypass, and signal low. REFerence is the white wire and it provides a square wave signal from the module to the ecm. EST is the purple / white wire that carries the timing signal from the ECM to the module. EST is also a square wave when the ECM is commanding timing. The Bypass wire is tan / black and you will read 5V on that wire when the ecm wants to control timing or zero volts when the ecm does not want to control timing. Black / red is signal low, a dedicated ground between the module and ECM. The wave you're describing sounds like ignition secondary pattern. Ignition secondary should not show up on the wires between ECM and distributor.

Just want to nip a possible point of confusion for anyone new to the GM ignition...

You have your REF and EST wire colours backwards. Purple/White is the REF wire, and send the RPM reference pulses, AKA "DRP" (Distributor Reference Pulse) to the ECM and the white wire is the return from the ECM to the ICM that controls the actual timing.

[1project2many]

Just want to nip a possible point of confusion for anyone new to the GM ignition...

You have your REF and EST wire colours backwards. Purple/White is the REF wire, and send the RPM reference pulses, AKA "DRP" (Distributor Reference Pulse) to the ECM and the white wire is the return from the ECM to the ICM that controls the actual timing.

You are correct, sir. Thank you for the correction.