Help with Insulation Test and DTC Codes

I have been trying to track down an issue with my daughters 2005 Prius. Her mother gave it to her and she started to have some issues with it about three weeks ago. I posted a thread when it originally happened. I have more information now but that thread seems to be dead now. Anyway here is a short history of the issue,

She had no problems with the car for about 8 months (since she received the car). It started throwing a code indicating there was a bad cell in the HV battery. A cell was replaced that had low voltage. The car ran for about two days with no issues. She drove it to a friend’s home and as she pulled into the driveway and the cars MFD and the instrument panel lights started displaying codes (MIL, triangle of death, ((!)) and a couple more. The car would not restart after this happened so she had the car towed to my home. The tow truck driver had a wheel lift truck and had to use a jump pack to get the car into neutral so it could be pushed into the street so it could be hooked up for the tow. It was towed ft wheels in the air, rear wheels on the ground.

When the car arrived I put the code reader on it that I had at the time. I also checked the voltage on the 12v battery with a load tester. It was showing 4 volts and a bad battery. It was replaced with a new Optima battery. The code reader I had wouldn’t show me enough information to try and track down the new issues.

I now have a better handle on the codes involved and they are P0AA6 with sub-codes 526 and 614 and C1310. From what I have found by reading posts this indicates the inverter might be bad but after putting an insulation tester on the circuits I am a little confused about what I am seeing.

1. With the HV cables disconnected from the master relay forward to the inverter (unplugged at the inverter) I get an almost immediate >550 M ohms using 500 volts on both cables.
   
   
2. All three terminals on the MG1, MG2 and A/C plugs (disconnected from the inverter) show > 550 M ohms but the ohms build slowly to that point.
   
   
3. The 4 HV terminals inside the inverter all show > 550 M ohms but they build slowly to that point with the inverter isolated (at least I think it is). If the larger terminal with the large number of wires is hooked together then the reading goes to 2.9 M ohms and 3 M ohms at the HV terminals where the HV cables from the rear of the car enter the inverter.
   
   
4. All four terminals of the main relay at the HV battery show > 550 M ohms when it is isolated from the battery ECU. However, if the red plug with all the sensing wires from the battery pack is connected to the ECU then I get a strange reading from the positive side of the main relay on the battery side. The reading will rise to a high M ohm reading but it is very very slow.
   

Anybody have any ideas because the readings seem a little strange considering the trouble codes. I have three short videos of the Meg Test but I cant seem to get them to upload so they will play correctly. If it helps I'll try to upload them again.

 

Thanks for the information. I thought that was probably what was going on but I really did not expect to see it act that way because of the HV battery ECU and none of the Insulation test results match what the codes indicate as a problem.

 

I found the problem. It is the top battery cable from the HV battery into the inverter. There is a metal ring around the inside of the plug that fits inside a metal ring that is bolted to the inverter case. There is a fault between the cable wires and that ring inside the plug. Do you know if the cable can be repaired or not. If not I'll have to find another cable. I'll try an upload a photos of what I am talking about.

 

Thanks, I will check it out

 

I have found by looking through a lot of the postings here that they never seem to have an end. Many times there is never a resolution to the problem and the thread dies. I wanted to end this one with a resolution.

There was definitely a fault on the upper cable at the inverter, in the plug for the HV + side cable. This was a little tricky to find because if you tested the cable from the battery forward with the cable connected to the inverter there was a fault showing. If you disconnected the cable then again checked the cable there was no fault. This led me to start looking at the inverter itself because the cable by itself showed no fault to the frame of the car. But when I inspected all the HV avenues inside the inverter I could not find a problem. I am sure if I had taken this to a dealer they would have just replaced the inverter (both MGs checked out ok as did the A/C).

This problem was caused because of a fault between the HV cable and the shield (I guess that is what it is) surrounding the inner wires at the inverter plug. After I replaced the cable with a new one (Actually a used one from eBay) the codes went away and the car runs fine. So if you run into these codes be sure to look at the HV inverter cables. The fault did not show up with a regular volt meter but using an insulation tester it showed right away. I updated the photo to show where to check.

 

I'll see if I can give you the reader digest version. I've done this once. The first thing is you have to pull the safety switch out of the HV battery to make it safe. You have to remove the cover from the battery so you can disconnect the cable. The rear seat needs to come out also. Then disconnect the cable from the inverter under the hood. You will need to get the car up on jack stands or a lift if you can get your hands on one, you will need to get under the car. On mine (2006) the cable runs along the bottom of the car covered by a black plastic skid plate from where the cable comes out of the bottom of the rear seat floor pan to where it runs up into the engine compartment on the drivers side. This is the most time consuming and frustrating part. There are a lot of small nuts and plastic retainers holding the skid plate on. I would suggest just spending some time looking at it and it will be apparent what you need to take off to get the skid plate off. The HV cable runs inside the plastic skid plate. Just take your time and buy a box of band-aides. PM me and I'll try to walk you through it. It is not too difficult but it will take a while and it does get pretty frustrating trying to feed the cable up into the engine compartment because there is not much room to work unless you take the inverter completely out. Good luck

 

When I replaced mine I did not have to do either of those steps. I did not have access to a manual when I did mine. You also need to keep in mind the manual wants you to remove the complete front end of the car to replace the head light bulbs. I would suggest just studying the cable layout in you vehicle and see if that is really necessary. The 2005 that I replace the cable on that was not the case.