P0A4C and P0A4D, plus random momentary complete loss of electric, plus smell

Something strange has begun on my (rebuilt) 2006 Prius.

I'm finding random short-lived electrical failures. Usually, it happens when the car is parked and off. Suddenly, everything electric just stops working -- for example, the "dome" light, the keyhole light, the little lights on the dashboard [door open, etc]. Everything goes dark. But, wait a short time -- seconds usually or the first time it took a couple minutes -- and it comes back on. The trip meters are reset to 0. The clock is reset to 1:00.

To be clear: there is NOT the Triangle of Death.

I get 2 error codes: P0A4C and P0A4D.

I took it to the local Toyota dealer, who looked at it for an hour or so and said, "Uh.... can't find anything wrong." So they updated my software and "recalibrated." This didn't do any good (of course).

So far, the problem has occurred maybe 8-10 times. At least once, it happened overnight; I only know because the trip meter and clock were reset. It has never happened while the car was running [thankfully!]. It is almost always when I first get into the car and try to start it. One time, it happened when I pulled into a gas station, and tried to turn Off the car. It didn't turn off! Instead, it hiccupped (electronically) and reset the trip meter & clock. Another press or two of the power button, and it then turned off.

The first time it happened, it was after the car had been sitting unused for a few weeks [coronavirus lockdown, you know]. I had driven no problem to a store, about 45 minute drive. I came back to the car, unlocked it no problem, got in, and before I could start the car, the dome light faded out (along with all the dashboard lights). I figured I was going to be taking the bus home. But, a couple minutes later -- my having done absolutely nothing -- the dome light (and dashboard lights) just came back on. It started and drove no problem, all the way back home.

The other factor worth mentioning is the smell. For quite some time (couple years) there's been a slight smell coming from somewhere around the hybrid battery. Specifically, it comes from the vent at the passenger side rear seat area. I took this to be a dirty fan exiting the battery compartment. I read somewhere [I think it was on the Prolong battery reconditioner's documentation] that that fan tends to get dirty. At the time, I couldn't figure out how to get to it, so I just left it. Anyhow, that peculiar smell is now suddenly notably stronger. Could be coincidence, but you figure it is probably connected.

The hybrid battery itself seems to be fine. Power level looks good. It has been a while since I reconditioned it with the Prolong. But the levels appear to be fine. (Meanwhile, the 12V battery is not new, but also not terribly old. Its level also seems fine.)

So, any ideas????

Thanks in advance!

 

Thanks for the quick reply!

I'm using a "Foseal" wifi OBDII reader, communicating to "Engine Link" app on an iPhone.

I'll check the 12V connections... I certainly didn't notice any problem when I tested its voltage level last week. But... worth a check.

I just now checked the battery fan. (It has only 1 clip. The Prolong instructions say it should have 3. Well... maybe because mine is rebuilt.) I also couldn't find any (easy) way to get the upper duct out of the way. Removing the clip, I can push it far enough away that I can peek down into the fan area. It doesn't appear to be caked over with crud or anything.

The odor is very mechanical smelling. well, smells are hard to describe in words. My brother, who lived decades in Japan, says it smells very much like the oil from something [I forget exactly what he said] on a Japanese train. I don't know how to describe it. But probably it's something either overheating or decaying [or both] -- something of the nature of oil or electronic components. Maybe. But it's been too long and is not like a dead animal smell, and there's been no standing water for a couple years now.

 

Now! There's an idea that I'd not even thought of. It does seem to happen when pressing the Power button. Hmm... I had thought that it happened one time when I just left it overnight -- but perhaps it actually occurred right when I turned it off, the night before.
On the other hand, the very first time it happened [just over 1 month ago], it was different. That time, I had definitely not pressed the button yet.
So... I'm not sure what to think about it. But it's worth paying attention to that, at least.

 

A COUPLE UPDATES

1. OK, I drove it again today, and thought how to describe the odor.

It's rather similar to gauze bandages. You know that classic smell of a Band-Aid? It's really quite similar to that.

2. Meanwhile, the problem did not recur, and the smell was markedly less today. I have no good explanation of why. All I did was putter around slightly with the battery fan. If that actually changed the situation, then... it's mighty fragile.

3. Also, I looked at the 12V connections and there is no obvious corrosion. I didn't have a chance yet to actually disconnect it and inspect the terminals (and ground) in detail. But if there's any corrosion, it must be small.

 

That's probably it, then -- for the smell, that is. I guess it doesn't, then, have anything to do with the electrical problem.

Is replacing those tubes easy?

 

OK, I finally got a moment to go inspect the 12V battery closely. No corrosion, but...

The cable on the negative terminal was quite loose; easy to just pluck it off the terminal with a finger. I.e., it was on the terminal, but was not clamped down. So... that's probably all the problem ever was. I say this without having put it to the test, you understand. So, time will tell. But I'm hopeful that that's all it was.

And that is mighty awful simple.

Ironically, if there hadn't been those 2 error codes that induced me to think there was a serious problem, I might have figured that out all on my own. Not only never posting here on PC, but also not wasting $140-some bucks at the local Toyota service shop. (Who, it must be pointed out, did not find the problem!!)

Well, on the plus side, I got the car's software updated. :-?

And, thanks to y'all, I now know what is causing the funny smell.

 

Yes, and I checked the 12V early on. The voltage is good (too long ago for me to recall specifically, but 12.X).

I plan to drive a bit today, and a bunch tomorrow. So we'll see how it goes.