HV Battery goes down in about 2-3 blocks Power Flow not operating normal

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I have two 01 peiuses. I been taking parts from #1 to try trouble shooting the other. # 1 runs good with HV Battery, I take the Battery out of it and put it in #2 it goes about 2-3 blocks and it pulls the HV Battery down an I end up with a P3010 code. I think the HV ECU is in the battery box an it has been changed out twice along with the HV battery. I think I have eliminated the HV Battery as the problem along with HV ECU. Does anyone know if the engine ECM could be doing this to me or have another idea of what I should change out for possible problem??? If I substitute the engine ECM, I will have to set up the handshake between the Transponder ECU and engine ECM. I've never done it before so I'm not too quick to jump in unless there is a good chance this may be the problem. I don't like the idea of having both cars in a non running status. I would really appreciate some ideas on this. Thanks much.