07 Gen 2 Triangle of Death Repair and Maintenance weekend!

I got the red triangle of death just under 3 weeks ago in my 2007 Prius Gen 2 (215K miles) and that started my search for a solution. The information I got here on Prius Chat was invaluable and pointed me in the right direction for an economical do it yourself fix. I appreciate it. Youtube videos really helped me be prepared for disassembly and putting things back together.

I got the Red Triangle of Death with a code of P0AFA(low hybrid battery voltage) read by my scanguage and started hunting down the problem. Various threads and researching of codes and then getting the DR Prius app and a Bluetooth OBD2 reader lead me to believe I either had a bad blade cell or most likely a problem with battery wire harness number 2(the one that senses the voltages of the battery blade pairs). The app was showing me occasional negative voltage readings and after a few negative voltage readings on #1 the triangle would pop up and the car would enter limp mode. Once the DR. Prius app gave me a P3000 code.

I replaced the 12 volt battery right away because it was over 7 years old and I was getting 10.3 volts when things were powered up and the hybrid battery was not supplying power to the 12 volt system. Sometimes a bad 12 volt battery will cause codes so I wanted to eliminate that possibility.

Last weekend I opened up the battery to take a look at the bus bars, fasteners, the wiring harnesses and determine if the Battery ECU had any visually obvious damage. There was a fair amount of corrosion on the fasteners, buss bars and the wiring harness tabs. The wiring harness #2 looked suspect and so I ordered one. The ECU looked good and the wiring harness #2 orange plug had no obvious damage. I took off the battery cooling fan and cleaned it by carefully washing it. It wasn't horribly dirty but good to just have it cleaned up well. I vacuumed the battery to try to pull out dust from between the blade cells. Then I reassembled everything and waited for parts.

I drove the car and reset the code every time I parked

A head light went out again and so I replaced the headlight bulbs using the removal of headlight method on Thursday night after work.

Friday I really tore in to things. I removed the battery from the car and set it on a bench to work on. I removed the Battery ECU and carefully inspected the socket finding extremely small discoloration on the end of one pin. There was no pitting or soot or white corrosion so I felt good about that. The ECU board was clean and like new. I removed all the buss bars and cabling and washed all the plastic pieces with soap and water and left out to dry in the sun. With a dry tooth brush I cleaned all the battery terminal studs. I also used compressed air and a vacuum to try to remove debris between the battery blades and suck up the bits of corrosion I had knocked loose. I measured the voltage of each cell and after sitting for about 18 hours the highest voltage was 7.95 and the lowest voltage was 7.91 with 7.93 being the most common voltage reading. Upon removal and inspecting of the wire harness #2 the tab that sits under the cabling connector the furthest away from the ECU fell off as it was disconnected from the wire. This is the problem I was looking for and was in alignment with the codes and readings I was getting. I installed new buss bars on the cut off side of the battery and reinstalled the cut off cabling and covered the buss bars with the plastic shielding. I installed the new wiring harness #2 with new buss bars and fasteners. The fasteners I had did not have the freely rotating washer attached to them like the stock ones so I had to take extra care not to bend the sensing wire tabs as I tightened them to the 42 inch pounds of torque required. After installing the plastic shielding and looking things over again I put the housing back on the battery pack and installed it in the car.

The test drive went great and no codes popped up and the red triangle of death did not occur. As writing this I have put about 60 miles on the car and all is good.

Saturday I changed the spark plugs and PCV valve, cleaned the throttle body and MAF sensor. I found oil in the bottom of the intake manifold so I mopped up what I could before I reinstalled the throttle body. Carb cleaner works way better on a throttle body than MAF sensor cleaner FYI. I am hopeful the new PCV valve lowers the oil consumption that was going on. I was going through nearly 2 quarts between 5K oil changes. The old valve was crusty so probably was not sealing. I should have installed a new water pump belt when I had everything apart but I have the tools to do that in the trunk with a new belt so in due time.

With the new plugs and cleaned MAF and throttle body the car is running better. Probably a bit of confirmation bias in there but the car feels much improved. The plugs definitely were showing their wear with erosion on the ground side.

I used all factory parts with the exception of the plated buss bars and fasteners. I would recommend the stock fasteners for the battery terminals and if I work on the battery again I will be finding those fasteners. I could have got a more inexpensive price on the battery wiring harness #2 if I had shopped around more instead of going to the nearest dealer.

I only lost 2 fasteners the whole weekend so that is a win. The second to last bolt jumped out of the socket as I was reinstalling the relay box on the firewall and warped off to a different galaxy apparently as magnet and flashlight could not find it. The plastic push faster for the plastic piece under the hood did the same and I replaced it with one I had on hand.

I'm pretty happy with spending a few hundred bucks for parts, tools and tech to save what would have been a huge bill at the dealership. It was a good weekend and the trusty Prius is back in good condition again.

 

Thanks for that correction. I’ll be going back in to the battery to replace the wire assembly that has the orange safety plug. I’ll retorque to that spec.