Hello PriusChat-ers! I have a 2006 Prius that threw the Check Engine light, red triangle, and displayed "Problem" on the MFD. I use Torque Pro to read codes and the only code is P3018 - weak battery block 8. I would not be surprised if this is the issue. It's still the original HV battery, and I had to replace one individual cell 3 years ago. This is the first battery-related issue since then. However ... the symptoms aren't the same as before. I have no P0A80 code. The car drives completely fine -- I am easily able to maintain 70+ mph speeds, although the engine is clearly working harder. 3 years ago, it would enter "limp mode". The maximum difference between the highest and lowest HV block is only 0.5V, even under load. The code fires at completely random times while cruising on the highway, not necessarily when speeding up (the code triggers roughly 5-10 mins after I clear it). The oil level is normal. I'm curious if this could be a false alert due to an old 12v battery. It's 6 years old and the voltage is fairly low - 11.9V at rest and ~14V while the engine is running. Anyone have insight into this or general advice? To be fair, it's completely possible I have both a failing HV battery AND 12V battery. I'm going to replace the 12V battery, but messing with the HV battery will be a hard stop for me.
Toyota doesn't publish the specs that would trigger a P30xx code, but it seems that the higher the battery block voltage difference is, then the less time is needed to trip a code. 1.5V (failed cell) will code almost immediately. If block 8 goes high under charge conditions as well as low during discharge- then it's likely another failing module. Posted via the PriusChat mobile app.
Welcome to PriusChat!! When you replaced the one module, did you also top balance the HV battery using a 'grid charger'? Do you currently have access to a grid charger? FYI : you're moderated until you've posted 5 times.
Unfortunately, no and no -- but I will look for threads to learn more about it. I put in the replacement module from eBay and crossed my fingers. The fact that it worked for three years is a miracle. Yep, that is what I'm seeing now. It turns out that a failing 12V was wishful thinking after all. After looking more carefully into the battery voltage & resistance log generated during a longer test drive today, block 8 voltage is fluctuating more rapidly and to more extreme values than the rest. Its resistance is markedly higher than the other blocks too. Thanks all for the replies. Now I have to decide whether to play whack-a-mole again with these cells. P0A80 hasn't fired yet but it's only a matter of time.
