Red Triangle and Code P0AFA causes?

I have a 2006 Prius with 165,000 miles. I put a new OEM Toyota hybrid battery at the beginning of June and the car has run as normal. A couple weeks ago after maybe 5 minutes on the road, we got the red triangle of death and assorted other lights. This was maybe the coolest weather we've had in a this fall (in the 50's). So we turned around and drove home. I plugged in my ScanGuage and found P0000. I reset it and the car was fine for about a week (the weather was a little warmer). One cool morning my wife started the car and the red triangle and other lights came on again, so she didn't drive it. I was leaning towards a failing 12V battery since it seemed to correlate with the colder weather. When I came back to town, I checked the codes and this time was P0AFA. I reset the codes and drove it tonight with no lights or codes coming on. However, it doesn't seem to be running properly. The IC engine ran constantly, but the MFD did not show charging when stopped. It went back and forth between charging and assisting while driving, but the battery level indicator did not move. It stayed about 3/4 full charge in stop and go about 4 or 5 miles each way.

I installed the hybrid battery myself. I did not use a torque wrench on any of the connections. It came with new leads from the battery to the junction. I did not have to mess with any of the bus bar connections except to connect the new leads. I have not checked for any corrosion on the ECU connectors or other locations as I read in some threads (those seemed to have immediate and not-resetting DTCs and often just replaced bad battery modules, so may be different problem). If I do, what would I clean those plugs/terminals with?

I checked the oil, engine coolant and inverter coolant levels, all are fine. The coolant has never been changed (I have an inverter coolant pump and coolant in the garage, but I haven't made time). Inverter pump seems to be working (I see turbulence in the coolant reservoir).

Suggestions? I don't have a lot of time to troubleshoot right now because we are getting ready to move (and will be driving this cross-country). But I don't want to take it to a shop and have them throw ECUs and other expensive parts at it if it is a bad connection.
Thanks!

 

Thanks for all the replies. When I replaced the HV battery, I did check for signs of water entry near the 12V and doesn't appear to happen. I drove it today, warmer and without heat. It seemed to operate normally--the ICE would shut off when stopped or coasting. Electric motor would drive the car at slow speed/slow accel. The battery level still did not change when I was watching-stayed about 3/4 charged, which doesn't seem normal to me. But that could be the change from not running the a/c now that summer is over.

I need to check the age of the 12V battery again, I don't remember how old it is. I have had the car about 5 years and never replaced it. I did remove the radiator cap to check coolant level. I added oil, too. My experience with the light and oil is the light would briefly flash on a turn when low on oil. I read some suggestions for the battery ECU, but the ones I read were not associated with intermittent or reset-able code. That doesn't mean it isn't the problem, but I'd like to rule out cheaper fixes first.

 

Update, after sitting 2 nights, I checked voltage. On ACC, the mfd showed 11.8v. On IGN-ON, lights on, fan on low, radio on, it showed 10.5v. At the terminals, nothing connected, it shows 12.3v. It is an OEM battery. If I found the right reference to date stamp online, I found printed on the sticker, below and at 90 degrees to the model number is 231010W. This appears to be manufactured October 23, 2010, right? FWIW, this battery has no "true start" label or anything, only GS YUASA.

I think I will replace the battery and see how it does.

 

Good deal on a 46 ah battery from NAPA--$148. But it didn't solve the problem. Still have the lights and P0AFA. Sometimes I have 4 lights--the red triangle, a yellow exclamation inside a circle and parens, VSC, and check engine. Sometimes only the red triangle and check engine. Mileage is down, too. MFD shows about 33 mpg average so far. About 9 or 10 lower than it usually shows. Any thoughts?

I'm preparing for a cross country move and don't have time to spend on this. How do I make sure the mechanic can properly diagnose it and not just swap parts until they find the right one?

 

I realize that and is why I said I need to take it to a shop. I was hoping for some helpful advice, maybe from someone who had a similar experience.

 

Thanks Bisco. If it isn't fully charged when installed, won't the car charge the battery? I waited a while to post in case it went away. It has been in the car for almost 2 weeks now, though I've only put 100 miles on it. The battery has a 10/18 sticker on it, whether that is manufacture or delivery, I am not sure. It was November when I purchased it.

 

Thanks for the info Bisco!

Ironically, my car may finally be charged. The light went off this afternoon on its own, and so far has stayed off. I would reset it periodically, but would always come back on. Hard to believe it charges so slowly, but with my experience, I don't think I'll ever bother with maintenance charging.

Have had the car 5 years and the battery lasted 7. For the last 4, we have been in the city and the car regularly sits for a couple days at a time and sometimes for a week or two. When we do drive it, most often it is for less than 10 miles. If a battery lasted 7 years with that kind of use, this battery will probably outlast my car.

 

I guess I jumped the gun. The next morning all the lights were back on. I guess it's time to get it to the shop...