Go figure!

Here is an interesting set of problems for the super-sleuths on this
forum. Three Gen I owners have been swapping parts trying to help each other out.

#1 – 2001 Prius:
Symptom: will not start (no ready light)
DTC P3105 - Battery ECU Communication Circuit Malfunction
DTC P3115 - System Main Relay Malfunction
Information codes not available.

#2 – 2002 Prius:
Symptom: will not start (after brief appearance of the ready light)
DTC P3125 - Converter & Inverter Assembly Malfunction
No information codes reported by an AutoEnginuity scanner.

#3 – 2003 Prius:
Symptom: will not start (no ready light)
DTC P3100 - HV ECU Malfunction (with information code 310)
DTC P3125 - Converter & Inverter Assembly Malfunction (with information codes 327 & 332)

When the traction battery from vehicle #2 was swapped into vehicle #1, the engine started, and the vehicle moved. Our tentative conclusion is that the Battery ECU in #1 is probably faulty since P3105 and P3115 did not re-appear with the other pack in the system. Battery #2 in vehicle #1 would not accept a charge, with the individual cells ending up, on average, 0.6V lower after the test. Would DTCs P3030 and P3006 from battery #2 prevent charging, or should we look further for a charging system problem in vehicle #1?

Based on black marks on the wires where the sense lines on battery #2 plug into the Battery ECU, we concluded that the sense line harness on battery #2 needs replacing. When battery #2 is in vehicle #1, DTCs P3030 and P3006 are generated, but when it is in vehicle #2, only DTC P3125 is generated. Therefore, the Battery ECU would appear to be working. Why would the codes be different when the battery is in different vehicles? Should we be looking for wiring harness problem between the HVECU and the Battery ECU that prevents any communications at all and thus blocks the other codes from being reported?

Swapping the inverter from vehicle #3 and also a spare inverter into vehicle #2 did not change the symptoms. Swapping a spare HVECU into vehicle #2 did not change the symptoms. Resistance measurements on the cables to the inverter from both MG1 and MG2 do not show any dead shorts, so a stator failure is not suspected. Any other ideas?

Swapping the inverter from vehicle #2 and also a spare inverter into vehicle #3 did not change the symptoms. Swapping a spare HVECU into vehicle #3 did not change the symptoms. Any ideas?

 

While we knew the harness didn't look good, we were not aware it wasn't functioning until after the first swap and seeing the new DTC pair.

We ran out of time yesterday to attempt that.

At this point, vehicle #1 seems closer to getting to the "no DTC" stage than the other two, and the owner ordered a battery ECU from TX this morning.