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Skyvisions, ASE Certified Technician
Category: Toyota
Satisfied Customers: 14422
Experience:  Toyota Master Diagnostic
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Customer Question

THIS QUESTION IS ONLY FOR MECHANICS WHO HAVE EXPERIENCE WITH PRIUS' I have a 2002 toyota prius. I purchased it with a bad hybrid battery. I have a backround in mechanical work and some experience rebuilding them (replacing bad cells etc). When I purchased
the vehicle it ran and had the red triangle and problem with main battery on the MPG screen. The vehicle DID run and Drive. I bought a used hybrid battery from a dismantler. I hooked up everything as before and now the car wont start. when I go to start the
lights on the MPG screen and the clock light dim and the vehicle wont start. I assumed it was the junkyard battery. brought it back, installed the old battery and the car still wont start! Im stumped! never had this much difficulty. checked the voltage on
the main (little battery) 11.8 hooked up with jumper pack, no start. Hooked up with another car and jumper cables 12.8 No start. I am getting a code P3115. but the car originally did run. So assuming the junkyard didn't do anything with my core while i had
their battery the car should still start.
Submitted: 1 year ago.
Category: Toyota
Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Skyvisions replied 1 year ago.

Was the P3115 code there with the original battery or was it only there with the used hybrid battery when it was installed? Does the code Ever clear? Do you know what this code means or how it sets?

Customer: replied 1 year ago.
Honestly I'm not sure. I didn't bother checking when I removed the original battery. From what Ive read its a system main relay code which can either be the relay or the hybrid ecu both of which are located inside the battery correct?
Customer: replied 1 year ago.
What I do know is the original battery in the vehicle main the ICE engine start, now it does not
Expert:  Skyvisions replied 1 year ago.

This code will set whenever the current sensor for the system main relay is either open or has failed. The sensor detects when there is current flow and the system main relay closes. The system main relays and the battery ECU are located within the HV battery on the one end. Make sure all your connectors are properly installed. There are three wires that communicate between the system main relay and the battery ECU they are as follows. At connector A or S8 pin number seven should be a yellow wire pin number two is a yellow with a black tracer and pin number six is a yellow wire with a red tracer. There are no other connectors between that system main relay and the battery ECU. At the battery ECU connector B pin number four is the yellow wire pin number 10 is yellow with black and pin number three is yellow with red. You should have less than .4 ohms of resistance from the system main relay pin corresponding with the same pin and color configuration at the battery ECU. Check your pin fits to make sure there tight make sure you have continuity on all three of these wires between the two components. If all of this checks good I would take the system main relay and battery ECU out of your old battery pack and put it with the used battery pack and see if that solves the problem. It's possible that could be corrosion or issues inside either one of these used components. That code will only set when the computer does not see the current sensor or the system main relay is not closed. I will submit an additional service which allows us to contact each other via telephone if you have further questions or need more detail it would be easier to discuss over the phone. You can accept this offer at any time.

Customer: replied 1 year ago.
Id prefer to keep this to a thread for now. I think you may have misunderstood the situation. We no longer have the battery we purchased. we returned it and have our original battery that we started with. (that the car was running with). So we have no parts to swap. We tested continuity from the specified pins all was good, yet I am somewhat confused. There are two connectors that go to the hybrid computer located in the battery, the other main connector goes up toward the front of the car. this is where we tested continuity from between these two connectors please refer the the pictures below.I looked on shopkey for this code and is said it can be caused by (as you said) a short in the wiring, bad system main relay or the hv ecu going bad.
I unplugged the 20amp HV fuse under the hood on the drivers side and the display screen read "problem solved" not sure if that gives you any clues. I suppose my main questions before I go purchasing parts are:A: there is a HV Control box which is located underneath the passenger side carpet and metal plate. Then there is of course the Battery ECU located in the actual battery. Which one is more likely to be causing this problem?B: Where exactly am I testing continuity from? Do the connectors need to be plugged in while im testing? Am I testing between the two connectors while they are disconnected from the battery ECU? If so everything tested good.C: When I go to turn the key to start the car I hear a clicking coming from the drivers side fuse panel between the door and steering wheel, yet no start, is this relevant or normal?Im still boggled as to why the car was originally running with this battery and now it is not. Im doubtful at this point is a short in the wiring. Im more so leaning towards the HV ECU or HV control unit going out. or while the battery was being transported the main relay or the assembly it lies in was damaged. All of which seem equally unlikely. In your opinion given the continuity is good. Where would you start?
Customer: replied 1 year ago.
Still Waiting on an answer. Id rather not lose a day on this.
Expert:  Skyvisions replied 1 year ago.

Sorry for the delay I was off for a couple of days. I will review this information this evening and get back to you. If you have solved the problem based on the information I have given you please let me know.