Hello everyone! I have a 2005 Prius that gave a P3030 code the other day after sitting for a few weeks (red triangle, check engine light and an explanation point). I did some research on this forum and checked the sensing wires on the battery pack. They had some corrosion on them and I decided to order a new harness from Toyota, the $100 seemed worth it instead of trying to repair the small gauge wires. After installing the new harness today the code is still present, I removed the battery again and did a continuity test on the wires from the terminal to the connector that goes into the ECU for each wire and they checked out good at close to 0 ohms. I inspected the ECU and there is nothing obvious there, the PCB has a good coating on it and no corrosion or burnt electronics. I’m at a loss what to do or check next, I have a basic OBD scanner that can check and clear codes but cannot see the individual cell voltages while the battery is installed. I’m willing to shell out the money for one to help diagnose if there are recommendations on what to get. The car drives fine and the energy usage screen shows the battery charging up while driving and the battery putting power to the drivetrain. Thanks in advance for any help. Dave
Getting a mini VCI cable (that comes with a bootleg copy of Techstream diagnostic software- amazon or ebay) is a good idea for anyone working on an older Toyota, esp a Prius. Another possibilty is to get a compatible OBD2 adapter and use an app like Dr Prius or (android) Hybrid Assistant - which let you see data from the battery ecu. Many here have both- vci and obd2. Posted via the PriusChat mobile app.
remove both harnesses and check individual battery voltage. I had this happen and the acid followed the sensing wires all the way to the controller where it shorted and burned off 4 or 5 pins inside connector on the controller
Pins getting messed up in that connector is a fairly common problem, but I'm not convinced the reason is electrolyte following the wires there all the way from the battery modules. As a minor point, but worth remembering, the electrolyte in the NiMH battery is a strong alkali—about as far from an acid as you can get on the pH scale.
Thanks for the replies, I would have replied earlier but I didn’t realize I had not set up notifications for the thread. I did check the ECU pins and they all looked good with only minor corrosion on them, no electrolyte present from any batteries and each cell measured around 8.3 volts or so, I opened up the ECU and did a continuity test from the outside connection pins to the solder joint joints on the PCB and it all checked out good. With a little more research I found a service bulletin stating if the continuity of the sensing wires check out ok then replace the battery ECU. I ordered a unit off eBay for less than $100 shipped, it had a different part # but said it was for an 04-09 Prius. I installed that today and it cleared the problem! Thanks for the suggestions.
