HV Battery Cell replaced and now will not start C1310 and ((!))

A little history. This is on a 2005 Prius with about 125,000 miles. The car belongs to my daughter and her mom gave it to her a few months ago. It had been running well until last week. It threw a code indicating low voltage in a cell in the HV battery (I forget the exact code but something like module 8). I pulled the HV battery and did find a cell with 6.67 volts. All the others were between 7.6v and 7.9v. The bad cell was replaced with a cell with 7.8v. I put it all back together and started it up. The triangle with the exclamation cleared itself and I did a couple of test runs in the car and had no problems. There were no other DTCs found. I buttoned the car back up and my daughter took the car home.

The next day she drove the car to a friends home (about 7 or 8 miles). When she got there she said she was having some problems. The triangle had returned and the warning lights for the ABS, Traction Control and MIL were all lit up. She also said she could not turn off the car. I went and put a scan tool on it and the only code I could pull was in the ABS module C1300. I couldn't get it to start and it would not jump start (the 12V battery was at 4 volts) so it was towed. I pulled the 12v battery and put it on a charger overnight.

The charger was able to bring it back to 12.8v and when I load tested it the voltage dropped to 11.5v and after 10 sec recovered back to 12.5v. I put the battery back in the car and checked it for codes because the car still would not start. The triangle was lighted and the ABS, traction control warning, BRAKE, and ((!)) were lighted now. I pulled three codes out of the ABS ECU, C0200, C0205 and C1310. I attribute the C0200 and C0205 codes to the tow. The car was towed with a wheel lift tow truck with the front wheels off the ground. I cleared the codes with the scanner but the warning lights remained on. The car would not start. I removed the neg terminal from the battery for a min or so then replaced it. The warning lights were gone and the car started. I put the car in drive and drove it about 10 feet and the triangle and the ((!)) light came back on. I was able to drive the car for a few miles but the warning lights remained on. I checked for codes and I had the C1310 in the ABS ECU. I did not find any other codes but I did notice that the gas gauge was only showing one bar and it was blinking (I know the tank was 1/2 full). The car would not start until again until I removed the neg terminal from the battery. This was even though I had cleared the code with the scan tool and it was showing no codes in any of the ECUs.

I went though about 4 or 5 cycles getting the same results and the same C1310 (HV system fault) code, triangle and ((!)) warning lights. On the drives the warning lights would stay off for up to about 10 miles before coming back on at the most and then once the car was shut off it would not start again and the warning lights would be back again. I did notice that the 12v battery was pretty much drained a couple of times but it would charge back up again when the car was started after sitting for a few minutes ( but only after disconnecting the neg terminal before trying to start it again). The scan tool show the 12v system is charging at 14 volts when the engine is on and 13.7 volts when the engine is not running but it is still in the run (ready?) state.

I have given up pretty much and need some ideas. Any help would be greatly appreciated

 

The 12v battery was replaced with a new battery but the same problem continues. I did find a loose connection on the HV battery connections leaving the HV battery and there were some signs it had arched between the contact and the loose nut. I cleaned those contacts and reconnected the batteries. It threw the same code again (C1310) again. I am not picking up any other codes. I am using a Autel Maxi Check scanner ( its a pretty good scanner). I looked at the video about the HV voltage leak and the code sets everytime about 15 seconds into the second stage (in ready mode with the transmission in neutral) the triangle and the ((!)) light along with the car and ! in the MFD. Wouldn't that be consistent with the loose battery connection I found? The saga continues

 

One other bit of information is the car will not set the code if the parking brake is set. The instant the parking brake is released (not the transmission park) the code will set. Also Brad you have no idea what my background is concerning high voltage and if you do not have anything constructive to say keep it to yourself. That nut was tightened to specs but I did not put any lock tight on it and it seems to have backed off just a hair. The solenoid/relay (or what ever it is attached to) is connected to very flimsy sheet metal and if you torque down on it too much the relay will rotate into the side of the battery case and bend the metal it is attached to. The cell that was replaced is not leaking and the 4th digit is an "H". I'm in the process of getting another scan tool but before the car initially set the code to replace the HV battery because of a bad cell there were no other problems with the car. My daughter had a perfect storm happen just after the battery with the weather changing really cold and the 12 v battery taking a dump. Right after the HV cell was replace I drove the car several times with no issues. The symptoms she had pointed straight to the 12v battery and an initial code for the anti skid ECU. That code went away when the 12v battery was fully charged which makes me think that the ECU was not getting the proper voltage and set that code. That code has not returned to the ABS ECU.

 

That may be true but that was not a helpful comment.

The codes I am getting do not seem to point to a HV leak though. The master caution light comes on whenever there is a safety problem not just a HV issue. Granted the C1310 code is indicating something with the HV system ( a fault of some kind). While it is true that just setting the master caution can indicate a HV leak, the Master caution and the ((!)) set at the same time does not. But, thanks for the feedback.

 

Thanks for the information. The reason I was wondering about the gas gauge was because the car was almost empty when the problem happened originally and I know from past experience with my daughters mom (who did run it out of gas once) the car will not run at all and throw codes. I have a diesel truck and if the fuel gauge shows no fuel (even if it is full and the sending unit is bad) the ECU will shut it down because it doesn't think there is enough fuel to do a regen on the DPF.

I have found from reading all the posts around that when a 12v battery dies it is common you cannot turn off the car because the computer can not detect if the transmission lock (or whatever it is called) is in the right position (that was also the message on the MFD at the time). At the time of the original problem (which happened a day and about 30 miles after the HV battery cell was replaced) the only code I found was on the ABS ECU and it was C1300 (that code disappeared after the 12v battery was replaced and has not comeback). The car was towed with a wheel lift tow truck (Ft wheels up and rear wheels on the ground). The dead 12v battery was replaced with a new Optima battery and I found codes from the front speed sensors but I am sure those were because the rear wheels were turning and the front ones were not causing the ECU to get confused. Those two codes have since gone away.

I have removed the HV battery and double checked everything and I can find no faults with it. I have a new scanner coming but the one I have allows me bi directional communication with a lot of the ECU modules in the car but I am not seeing any secondary codes so I will recheck that when the new tool gets here. The only obvious errors are the master caution and the ((!)) along with the car and ! on the MFD. I have notice that this is a real common issue after a HV battery replacement (rebuild, cell replaced, etc) but all the threads end with no resolution or with "the car set for a few days and I haven't had any problems lately.

 

The code is P0AA6 with a sub-code of 526. There is also a C1310 code from the in the ABS ECU with no sub-codes and the A/C ECU is throwing B1421 (but I don't think that has anything to do with the HV issue). Seems to point to the transmission. Could improper towing have anything to do with it?