I believe that not seeing 2.3v there is a sign of one of two things: AMM (unlikely since you already replaced it) but possible if you got one from a scrap yard! or the harness. You should run a continuity test between that harness and where it connects to the ECU. Using a wire diagram and an ohm meter, make sure there is good continuity between those wires and the one at the ecu panel on the passenger right foot panel. Also note that you are testing to make sure there is no continuity in ones that shouldn't have continuity.

You could do this first; unplug the ECU, set your multi meter to OHMS and make sure none of the pins have continuity to each other. If you find any of them do, you have a short and it is likely the problem.

If you find that the harness is in need of replacement, run new wires from the connector to the ECU connector. I'd just abandon the old wires and move forward. Make sure you are certain of your wiring diagram before you do this.
Alternatively, IPD sells whole wiring harnesses for around 300.
B