So my Prius has had the triangle of doom and later check engine symbols for a few years now. Normally it has codes P3000, B2799, and P3006. Performance-wise, it's OK, except sometimes when I hit the accelerator it doesn't go for a few seconds, then slowly speeds up. Nothing major. I recently took it on the highway and barely made it home! Symptoms included: 1. Triangle, check engine, and parking brake symbol that won't go away regardless of the position of the parking brake (though I could tell it was mechanically working just fine). 2. HV battery fell to 25% on the monitor and engine would NOT recharge it. 3. Engine on ALL the time at high revs. 4. Sometimes engine would work fine, other times it would take a while for it to speed up. When I got to the hill near my home, I barely made it up the hill as the car would jerk forward repeatedly, BARELY making any progress uphill! I barely made it. Without shutting down the car, I plugged in the laptop and got these codes: P0300 P0301 P0303 P3000 B2799 P3006 P3009 P3018 P3027 C1259 prius-doomed — ImgBB I cleared the codes, shut down and restarted the car and let the engine run for a few minutes. Then the only codes were: P3000, P3006, C1259 (new code). After clearing the codes, the bizarre emergency brake symbol functioned normally, being on only while the parking brake was actually engaged. I see those are multiple misfire symbols, but I have not noticed the car ever misfiring before and mileage-wise the plugs are one of the NGK or Denso double platinums recommended for the car. I think they're probably only 30k miles old at most, no way they failed both at the same time! So was this just a fluke in the computer and restarting it/clearing the codes helped or is it time to retire the car?
PP, my first guess from your codes & symptoms is that you may have either (1) a failed cell (or cells, plural) in the battery pack which is preventing the BIG HV traction battery from charging, or (2) a problem in the recharging system - might be a consequence of (1). The C1259 code means that the regenerative braking system (which captures energy from braking and feeds it to the HV battery) isn't working properly, which might be a consequence of (1). Diagnosis: pull the HV battery and inspect. Then choose to repair or replace.
First, it is time to check your 12 V battery and it's connections. It sounds like your HV battery is failing but you MUST first be sure that the 12 V system is good.
Should be good. Was replaced a few years ago. The previous one worked for twice as long I believe. Anyway, I'm being pressured to just buy a new car (too many issues for too many years), so I'll see if it's worth it to troubleshoot this one.
I wouldn't assume anything about either of the batteries. Which one was replaced a few years ago? The 12V aux or the HV?
The 12V, under suspicion of bad 12V due to strange computer readings (turned out to NOT be 12V's fault; was a bad computer, which was replaced and fixed the problem). I think I'm the third or fourth owner of this car. In between owners it has spent some time unused under the snow for months at a time in used car dealer hands, being juggled between auctions and private used car dealers, and recently has been driven once or twice a week. The weather is very hot and humid here, by the way, which in the past has triggered the orange triangle. Orange triangle would reliably come on in hot weather - a condition that began about 6 years ago. About 2-3 years ago, it reliably started getting the check engine symbol, but the code associated with it was actually a hybrid code. About 1-2 years ago, it started performing badly; I'd hit the accelerator and it would just stand there, but would start to go 3-4 seconds later (slowly). About half a year ago I started getting the turtle symbol occasionally. As far as I know, HV battery has never been replaced, but again, I am not the original owner. I do know that the HV battery was completely drained at least once about 4 years ago after the 12V was replaced. I was recently getting rapid SOC changes where the SOC would go from 3/4th to 1/4th within a minute or two while the car was parked. In the most recent drive, when I had the problem, it barely made it uphill. The engine would rattle awfully as the car inched up the hill.
I'm betting dollars to donuts that you need a new HV battery. I'd assume that you're getting your SOC info from the dash display. For $20 or less you can get a little Bluetooth OBD dongle and download the Dr. Prius app for free. (Free for Gen 1 b/c it doesn't have full functionality). The Dr. Prius app will tell you pretty much all you really need to know about the HV battery at this stage. A mountain above that would be a Techstream knockoff. It's the official Toyota diag system. Search this site and you'll find tons of info about it. But I would also have the 12V load tested. Things like misfire codes (e.g. the P03xx codes) have nothing at all to do with the HV batt. But they could have to do with the 12V. OR with other "normal" stuff, like old spark plugs. Do you plan to work on this car? If not - I'd probably join whomever says you just get a new car.
That is NOT valid logic. "should be good" often costs people LOTS of money.......when they find out much later that it is NOT good. Batteries fail at different times; sometimes even when brand new.
My son's prius had a problem going up a hill the other day. When the car is turned on make sure the invertor pump is running. Look for movement in the invertor reservoir. It the reservoir is between the engine and the invertor. Take the lid off and look inside for fluid movement.
