still wouldn’t condemn the ECM yet. The main thing that gets my attention is the 2976 code for DEF dosing unit temperature erratic. Since it stayed there even after trying another dosing unit, I’d be looking hard at the circuit, connector pins, and harness before calling the ECM bad. The 3558/3559 codes also make me think it could be a wiring or load issue. Voltage can look good with a meter, but the circuit can still fail under load. I’d load-test the wires, check pin drag/tension at the ECM and dosing unit connector, and watch the dosing unit temperature PID while doing a wiggle test, especially near the ECM and hot areas around the engine. Also check ECM powers and grounds with the engine running, not just key on. Bad grounds or voltage drop can cause weird random aftertreatment codes. If the harness passes under load, connectors are clean/tight, powers and grounds are good, calibration is current, and a known good dosing unit still gives the same 2976/3558/3559 behavior, then I’d start suspecting an internal ECM issue. But I’d want to prove all that first before replacing it.