GEN 1 prius P3106 powertrain code and vehicle stalls

P3106 involves communication between the HV ECU (kind of the orchestra conductor for the car) and the ECM (which controls the engine). I would expect weird results if those two aren't getting along.

There are some three-digit INF codes you can get with P3106, by looking in the code's "freeze frame" (using a scan tool that can do that).

if the INF code is 209, 210, or 211, the manual says to check the actual comm wiring (pin 28 of connector H14 at the HV ECU to pin 28 of connector E9 at the ECM, and pin 27 of H14 to pin 27 of E9), and if a wiring fault isn't found, to replace the ECM.

If the INF code is 212, it's not so much the communication circuit as what was communicated. The ECM said "something is wrong" and the HV ECU heard it just fine. Manual suggests saving the current HV ECU codes and freeze frames, clearing codes, and proceeding with troubleshooting of any DTCs the ECM itself might be reporting.

If the INF code is 394, the ECM seems to be asleep on the job. Check the circuit(s) bringing power to the ECM (after first saving codes and freeze frames and clearing, as above). If no problem is found with power to the ECM, replace the ECM.

The repair manual and the wiring diagrams (to consult for some of the electrical tests above) can be accessed as described here:

Toyota Service Information and Where To Find It | PriusChat

As for the blinking fuel gauge segments, see this post. (It summarizes "fuel gauge diagnosis check" under "diagnosis - combination meter system" in the repair manual, so if you get access to the repair manual, the information is all there.)

 

There's only one ECM in the car. There are several ECUs (ECU is the generic term, electronic control unit) but only one of those is the Engine Control Module. Yes, it's behind the glove box.

ECUs are made of silicon and go bad about as often as rocks do, so I probably wouldn't just replace it unless I had done the other troubleshooting and that's what was left.