I have a 2004 Prius with 184,000 miles. In the past few months it has started having a problem that has gotten increasingly worse. When I push down on the gas pedal, the car idles for about a full second before jolting into accelerating. Today, the car freaked out and a bunch of warning lights went off. I took it to the shop and they topped off the oil and sent me on my way. But the issue has not been fixed. The gap in time is still present, if not worse. Then when I put the car in park, the red triangle of death flashes once then disappears. Another thing I have noticed is that the car has generally been louder lately when sitting still or moving slowly. Times when it normally is very quiet, it sounds like the engine is working really hard. I called the shop back and they said it's most likely the hybrid battery needs to be replaced. This sounds reasonable because of the car's age, but if there's anything else it could be, I'd like to try that first.
It might be advisable to clean the throttle body and also the MAF sensor. The disconnect the 12 V battery again after doing both those things so the ECM can relearn the idle throttle position. Search Gen 2 forums using the Advanced Search options (click on the "More..." button on the search pop-up) or use Google to search using this string: Code: site:https://priuschat.com/forum/ Gen 2 MAF Cleaning I hope that helps.
Hybrid battery probably failing. Disconnecting the 12v made the computer forget that it should act like the battery is failing. It'll probably drive okay for a while and then do the same thing again. Lots of people limp it through a few loops like that for a while. Can't be certain without a real diagnosis, but it's likely that you are on borrowed time to make plans for a replacement battery or a replacement car.
That likely won't last long. You really need to get both batteries tested at a qualified shop. If the 12 V is over 5 years old, it should just be replaced.
That is a bit of a stretch, LJ, what you seem to be leaning toward is a ground isolation fault, which is not supported by the reported symptoms. I also don't see explicit signs of bad HV battery, so the OP should tread with caution. The best bit of your advice is to read the codes and then there will be more certainty of where to focus.
I made no such specific inference, and this isn't the first time you've incorrectly read in more than I've written out. I'm glad we can agree that a more thorough hands-on diagnosis should be the next step.
Thank you everyone for your thoughts. I ended up replacing both batteries which of course cost quite a bit of money. However, we are now almost 2.5 months in and the problem seems to have resurfaced. It appears to happen when I haven't driven the car for a few days and also if it is left parked in temperatures over 90. If the batteries are new, what could be the problem? I'll take it to another shop and hopefully they can solve it, but I'd rather not keep pouring money into this if it sounds like a lost cause.
Was the new 12 V fully charged before being used ? Is the HV battery really "new" or is it an old one rebuilt or "refurbished" ??
